10.1. Modbus RTU over Serial¶

Modbus RTU is a serial communication protocol that allows devices to communicate over the provided serial interfaces (USB and RS-485). The following connection settings must be used to connect to Modbus RTU on Magna-Power products:

Baud Rate: 115200

Parity: None

Data Bits: 8 bits

If the serial connection settings are configured incorrectly, Modbus messages may result in framing or CRC timeout errors. Further information about framing errors can be found in Error Handling.

Bit Allocation - Read Holding Registers (Function Code = 0x03)

Slave Address	Function Code	Starting Address (Hi)	Starting Address (Lo)	Register Count (Hi)	Register Count (Lo)	CRC (Lo)	CRC (Hi)
0-7	8-15	16-23	24-31	32-39	40-47	48-55	56-63

Bit Allocation - Write Single Register (Function Code = 0x06)

Slave Address	Function Code	Starting Address (Hi)	Starting Address (Lo)	Write Data (Hi)	Write Data (Lo)	CRC (Lo)	CRC (Hi)
0-7	8-15	16-23	24-31	32-39	40-47	48-55	56-63

Bit Allocation - Write Multiple Registers (Function Code = 0x10)

Slave Address	Function Code	Starting Address (Hi)	Starting Address (Lo)	Register Count (Hi)	Register Count (Lo)	Byte Count	Data (Hi)	Data (Lo)	Data (Hi)	Data (Lo)	CRC (Lo)	CRC (Hi)
0-7	8-15	16-23	24-31	32-39	40-47	48-55	56-63	64-71	72-79	80-87	88-95	96-103

10.2. Modbus Terminology¶

Slave Address: Address of the device to be communicated to. See Device Addressing Mode for details
Function Code: Defines the type of action to be performed by the device. See Functions for details.
Starting Address Hi/Lo: High/low bytes of the register address the command is referencing. In Table 2, this is listed as the Address.
Register Count Hi/Lo: Number of registers that the command is referencing. In Register List, this is listed as the Register Count. Ex. A register count of 2 should have a Hi value of 00h and a Lo value of 02h
Byte Count: Number of bytes referenced by the command. This number should be twice the Register Count.
Register Value Hi/Lo: High/low value of what is stored in the registers. See Data Format to see how this data is formatted.
CRC Lo/Hi: Cyclic Redundancy Check low and high bytes.

10.3. Device Addressing Mode¶

Modbus supports unicast and broadcast addressing modes.

In unicast mode request and response messages are sent by a master and slave nodes , respectively. In the master request, the slave address must be included to receive a response from a listening slave device. Magna-Power has this address set to 1.

In broadcast addressing mode, the master sends a request to all listening slaves, but none will respond. The slaves process the message and await the next request. To send a request in broadcast mode, the slave address must be set to 0.

10.4. Functions¶

Modbus protocol requires a function code, describing read write operations in the second byte of a message. In Table 1, a list of supported function codes and their uses are shown.

Table 1: Modbus Function Codes

Function Code	Name	Use
03 (0x03 Hex)	Read Holding Registers	Read 1-2 16-bit register(s)
06 (0x06 Hex)	Write Single Register	Write to 1 16-bit register
16 (0x10 Hex)	Write Multiple Registers	Write 2 16-bit registers

10.5. Data Format¶

10.5.1. Data Order¶

The order in which data is sent or received by the devices is a big-endian system, where the most significant 16-bit register should be sent first, and the following bytes should also go in order of most significant to least significant.

For example, the decimal value 123456789 (0x075BCD15 in hexadecimal), would be constructed and sent as a Modbus message as first 0x07, then 0x5B, 0xCD, and finally 0x15.

10.5.2. Floating Point Numbers¶

When reading or writing a register with a floating-point data format, as listed in Register List, the data should always be represented using IEEE-754 floating point notation, following the data order outlined in Data Order. For example, writing a value of 3.0 to a register should be sent in a Modbus message as 0x40, 0x40, 0x00, and 0x00.

10.6. Error Handling¶

Slave devices will respond with an error message if the request was not properly formatted for Magna-Power’s Modbus implementation. The first byte of this error message will be a number above 0x80. The second byte will be the exception code, which identifies the type of error encountered. In Table 3, the possible exception codes that can be received are listed.

Table 3: Modbus Exception Codes

Code	Name	Causes
0x01	Illegal Function	A currently unsupported function code has been sent. See Functions for supported function codes.
0x02	Illegal Data Address	The number of registers specified in the message does not match. See Register List for register count. The register address and function code do not match any commands. See Register List for command list.
0x03	Illegal Data Value	The register count is outside the allowed count. Modify the register count to be 1-2 registers. The register count and byte count conflict. The number of bytes is two times the register count.

Slave will not respond under certain addressing modes and when a request is malformed or corrupted. Non-response can happen when:

The queue has overflowed. To prevent overflow, allow more time between Modbus requests.

The message is corrupt. This happens when the message’s calculated CRC does not match the sent CRC, which can occur because of electrical noise or malformed messages. Ensure your software forms messages properly, using the correct byte ordering, and is calculating CRC correctly. Modbus CRC is sent low-order byte followed by high-order byte and is calculated using CRC-16.

There is a framing error. This can happen when the serial connection is incorrect or if there is electrical noise. Refer to Modbus RTU over Serial on the proper serial configuration.

The device is in broadcast addressing mode. By design slaves should not respond in broadcast since slaves’ response messages would trample each other on the network. Verify that the slave address is set to 1 if a response is needed.

10.7. Communication Examples¶

The ALx Series must be explicitly configured to communicate using the Modbus protocol. The factory default is SCPI Command Set, but can be changed from in the front panel menu Communication Setting-Command Protocol by selecting Modbus. Modbus messages are binary and traditional terminal programs (e.g., PuTTY, HyperTerminal) design for ASCII serial can not be used for communicating with ALx Series. For all the following examples, the open-source Modbus specific program, QModMaster was used to construct messages. Each example outlines a function, its arguments, the request, and the expected response. A screen capture showing field entries in QModMaster are also shown below.

10.7.1. Example Request Source Setpoint¶

Request		Response
Slave Address	0x01	Slave Address	0x01
Function Code	0x03	Function Code	0x03
Starting Address Hi	0x80	Byte Count	0x02
Starting Address Lo	0xB0	Register Value Hi	0x00
Register Count Hi	0x00	Register Value Lo	0x00
Register Count Lo	0x01	CRC Lo	0xB8
CRC Lo	0xAC	CRC Hi	0x44
CRC Hi	0x2D

../../../../../../_images/modbus-qmodmaster-sourcesetpoint-read.png

10.7.2. Example Set Front Panel Lock¶

Request		Response
Slave Address	0x01	Slave Address	0x01
Function Code	0x06	Function Code	0x06
Register Address Hi	0x80	Register Address Hi	0x80
Register Address Lo	0x30	Register Address Lo	0x30
Register Value Hi	0x00	Register Value Hi	0x00
Register Value Lo	0x01	Register Value Lo	0x01
CRC Lo	0x61	CRC Lo	0x61
CRC Hi	0xC5	CRC Hi	0xC5

../../../../../../_images/modbus-qmodmaster-lock-write.png

10.7.3. Example Write Current Setpoint to 5.00¶

Request		Response
Slave Address	0x01	Slave Address	0x01
Function Code	0x10	Function Code	0x10
Starting Address Hi	0x30	Starting Address Hi	0x30
Starting Address Lo	0x10	Starting Address Lo	0x10
Register Count Hi	0x00	Register Count Hi	0x00
Register Count Lo	0x02	Register Count Lo	0x02
Byte Count	0x04	CRC Lo	0x4F
Register Value Hi	0x40	CRC Hi	0x0D
Register Value Lo	0xA0
Register Value Hi	0x00
Register Value Lo	0x00
CRC Lo	0xB3
CRC Hi	0x40

../../../../../../_images/modbus-qmodmaster-setpointcurr-write.png

10.7.4. Example Request Current Setpoint (5.00)¶

Request		Response
Slave Address	0x01	Slave Address	0x01
Function Code	0x03	Function Code	0x03
Starting Address Hi	0x30	Byte Count	0x04
Starting Address Lo	0x20	Register Value Hi	0x40
Register Count Hi	0x00	Register Value Lo	0x9F
Register Count Lo	0x02	Register Value Hi	0xFF
CRC Lo	0xCA	Register Value Lo	0x60
CRC Hi	0xCE	CRC Lo	0x9E
		CRC Hi	0x05

../../../../../../_images/modbus-qmodmaster-setpointcurr-read.png

10.8. Register List¶

The Modbus protocol consists of requests to specific register addresses stored in memory. Each register contains stored value in memory that can be read from or written to. When a Modbus request is sent by a master to a register address, the listening slave device will respond in one of two ways. If the master’s request was a read operation, the slave device will respond with the value stored at the register that was read. If the master’s request was a write operation, the slave device will set the registers to the requested value and will respond with a confirmation that the registers were written to.

For instance, if the current set point needs to be read, the request message must specify the register address 0x3020, and the listening slave device will respond with its current set point value. Table 2 lists all the register addresses.

Modbus Command	Write Address	Read Address	Description
Operation Commands
StatusQuesQ	N/A	0x10B0	Returns the value of the Questionable Status register
StatusRegQ	N/A	0x10D0	Status Register
Input	0x1110	N/A	Enables or disables the DC input based on parameter setting
Measurement Commands
MeasCurrQ	N/A	0x2010	Measures and returns the average current at the sense location
MeasVoltQ	N/A	0x2020	Measures and returns the average voltage at the sense location
MeasPwrQ	N/A	0x2030	Measures and returns the instantaneous DC power at sense location
MeasResQ	N/A	0x2040	Measures and returns the instantaneous resistance at sense location
Setpoint Commands
SetpointCurr	0x3010	0x3020	Sets the current set-point
SetpointVolt	0x3030	0x3040	Sets the voltage set-point
SetpointPwr	0x3050	0x3060	Sets the power set-point
SetpointRes	0x3070	0x3080	Sets the resistance set-point
Trip Commands
OverTripCurr	0x4010	0x4020	Sets the over current trip (OCT) set-point
OverTripVolt	0x4030	0x4040	Sets the over voltage trip (OVT) set-point
OverTripPwr	0x4050	0x4060	Sets the over power trip (OPT) set-point
UnderTripVolt	0x4070	0x4080	Sets the under voltage trip (UVT) set-point
Slew Commands
RiseRampCurr	0x5010	0x5020	Sets the rising slew rate for current when in current regulation state
RiseRampVolt	0x5030	0x5040	Sets the rising slew rate for voltage when in voltage regulation state
RiseRampPwr	0x5050	0x5060	Sets the rising slew rate for power when in power regulation state
RiseRampRes	0x5070	0x5080	Sets the rising slew rate for resistance when in resistance regulation state
FallRampCurr	0x5090	0x50A0	Sets the falling slew rate for current when in current regulation state
FallRampVolt	0x50B0	0x50C0	Sets the falling slew rate for voltage when in voltage regulation state
FallRampPwr	0x50D0	0x50E0	Sets the falling slew rate for power when in power regulation
FallRampRes	0x50F0	0x5100	Sets the falling slew rate for resistance when in resistance regulation state
Control Commands
PowerRange	0x6010	0x6020	Enables extended power range
ControlMode	0x6030	0x6040	Sets the control mode
Function Generator Commands
FuncType	0x7010	0x7020	Sets the desired function for the integrated function generator
FuncSinAmpl	0x7030	0x7040	Sets the amplitude for the sinusoid function
FuncSinOff	0x7050	0x7060	Sets the DC offset from zero for the sinusoid function’s midline
FuncSinPrd	0x7070	0x7080	Sets the period for the sinusoid function
FuncSquLoLevel	0x7090	0x70A0	Sets the low level amplitude for the square function
FuncSquHiLevel	0x70B0	0x70C0	Sets the high level amplitude for the square function
FuncSquLoPrd	0x70D0	0x70E0	Sets the period that the square function remains at the low level amplitude
FuncSquHiPrd	0x70F0	0x7100	Sets the period that the square function remains at the high level amplitude
FuncStepLoLevel	0x7110	0x7120	Sets the low level amplitude for the step function
FuncStepHiLevel	0x7130	0x7140	Sets the high level amplitude for the step function
FuncRampLoLevel	0x7150	0x7160	Sets the low level amplitude for the ramp function
FuncRampHiLevel	0x7170	0x7180	Sets the high level amplitude for the ramp function
FuncRampRisePrd	0x7190	0x71A0	Sets the period for the ramp function to transition from low to high level amplitude
FuncRampFallPrd	0x71B0	0x71C0	Sets the period for the ramp function to transition from high to low level amplitude
Configuration Commands
FactoryRestore	0x8010	N/A	Restores the factory EEPROM data
Lock	0x8030	0x8020	Locks and unlocks the product from configuration and set-point changes
SenseMode	0x8060	0x8070	Configures the sense location and automated compensation values
SetSource	0x80A0	0x80B0	Sets the setpoint source

The Magna-Power implementation for Modbus limits reading/writing to one value (one to two registers) at a time. These registers must be adjacent in memory. For example, for measuring both current and voltage, two separate requests from the master device are needed – one for current and one for voltage.

10.8.1. Operation Commands¶

10.8.2. StatusQuesQ¶

This command queries and returns the values of the Questionable Register. This read-only register holds the live (unlatched) questionable statuses of the MagnaLOAD electronic load. Issuing this query does not clear the register. The bit configuration of the Questionable Register is shown in the table below.

Address: 0x10B0
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Integer

Questionable Register

Bit	Weight	Abbreviation	Description
0	1	OVP	over voltage protection, hard fault
1	2	OCT	over current trip, soft fault
2	4	OVT	over voltage trip, soft fault
3	8	OPT	over power trip, soft fault
4	16	OCP	over current protection, hard fault
5	32	OTP	over temperature protection, hard fault
6	64	RSL	remote sense loss, hard fault
7	128	CC	constant current regulation, regulation status
8	256	CV	constant voltage regulation, regulation status
9	512	CR	constant resistance regulation, regulation status
10	1024	CP	constant power regulation, regulation status
11	2048	SFLT	soft fault, the ord value of all soft faults
12	4096	HFLT	hard fault, the ord value of all hard faults

10.8.3. StatusRegQ¶

This command queries the Status Register. This read-only register holds the live (unlatched) operation status of the MagnaLOAD electronic load. Issuing a query does not clear the register. The register location and definitions are subject to change after any firmware release to accommodate new features. The Questionable Register is a subset of the status register and does not change between firmware updates. The present bit assignments are shown in the table below.

Address: 0x10D0
Function Code: 0x03
Access: Read
Register Count: 4
Data Format: 32-bit Integer

Status Register

Bit	Name	Description
0	standby	output is in standby
1	live	output is active
2	nonhalt1	available
3	nonhalt2	available
4	overCurrTrip	over current trip
5	overVoltTrip	over voltage trip
6	overPwrTrip	over power trip
7	remoteSenseLoss	remote sense voltage outside of acceptable bounds
8	underVoltTrip	under voltage trip
9	shutdown	target is creating a shutdown condition
10	linPwrLim	power across linear modules exceed ratings
11	resPwrLim	power across resistors exceed ratings
12	bootFailure	one or multiple target did not boot up
13	bootState	one or more targets are waiting to boot
14	phaseCurr	rated phase current exceeded
15	comm	communications are corrupted
16	overCurrProtect	terminal current exceeded product rating
17	overVoltProtect	terminal voltage exceeded product rating
18	tempRLin	linear module exceeded temperature
19	blownFuse	fuse is blown on the auxiliary power supply
20	interlock	interlock open
21	haltUserClear	available
22	maintenance	maintenance
23	tempDMod	diode modules exceeded temperature
24	incompatibleSysConfig	incompatible system configuration
25	stackOverflow	exceeded firmware stack
26	lineFault	line fault analog/digital inputs
27	tempRMod	resistor module exceeded temperature
28	belowRatedMinVolt	below minimum voltage rating(28)
29	outOfRegulation	out of regulation, unexpected currents measured
30	targetUpgrade	mainctrl upgrading other targets
31	haltSelfClear	available
32	phaseLoss	one or more phase missing
33	blownFuseInput	input fuse blown on fuse/emi filter
34	fanLockedRotor	one or more fan’s rotor has locked
35	notUsed29	available
36	tempPwrMod	power processing module temperature fault
37	tempOutputMod	output filter module temperature fault
38	tempOutputCap	output capacitors temperature fault
39	notUsed25	available
40	notUsed26	available
41	notUsed27	available
42	notUsed28	available
43	notUsed1	available
44	notUsed2	available
45	notUsed3	available
46	notUsed4	available
47	notUsed5	available
48	invalidSysRating	invalid system rating
49	notUsed7	available
50	notUsed8	available
51	notUsed9	available
52	notUsed10	available
53	notUsed11	available
54	notUsed12	available
55	notUsed13	available
56	notUsed14	available
57	notUsed15	available
58	notUsed16	available
59	notUsed17	available
60	notUsed18	available
61	notUsed19	available
62	notUsed20	available
63	notUsed21	available

10.8.4. Input¶

This command enables or disables the MagnaLOAD electronic load input. The state of a disabled input is a high impedance condition.

Address: 0x1110
Function Code: 0x06
Access: Write
Register Count: 1
Parameters: 0 (OFF) | 1 (ON)
Data Format: Boolean

10.8.5. Measurement Commands¶

10.8.6. MeasCurrQ¶

This query commands the MagnaLOAD electronic load to measure and return the average current through the DC terminals.

Address: 0x2010
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.7. MeasVoltQ¶

This query commands commands the MagnaLOAD electronic load to measure and return the average voltage at the DC terminals. If the remote sense function is used and engaged, this command returns the voltage measured at the sense terminals.

Address: 0x2020
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.8. MeasPwrQ¶

This query commands commands the MagnaLOAD electronic load to measure and return the average power at the DC terminals.

Address: 0x2030
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.9. MeasResQ¶

This query commands commands the MagnaLOAD electronic load to measure and return the average power at the DC terminals.

Address: 0x2040
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.10. Setpoint Commands¶

10.8.11. SetpointCurr¶

This command programs the current set-point that the MagnaLOAD electronic load will regulate to when operating in constant current mode.

Address: 0x3010
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x3020
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.12. SetpointVolt¶

This command programs the voltage set-point, in volts, which the MagnaLOAD electronic load will regulate to when operating in constant voltage mode.

Address: 0x3030
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x3040
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.13. SetpointPwr¶

This command programs the power set-point, in watts, which the MagnaLOAD electronic load will regulate to when operating in constant power mode.

Address: 0x3050
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x3060
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.14. SetpointRes¶

This command programs the resistance set-point, in ohms, which the MagnaLOAD electronic load will regulate to when operating in constant resistance mode.

Address: 0x3070
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x3080
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.15. Trip Commands¶

10.8.16. OverTripCurr¶

This command programs the over current trip (OCT) set-point. If the input current exceeds the over current trip set-point for multiple samples, the input is disconnected and an OCT fault is indicated.

Address: 0x4010
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x4020
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.17. OverTripVolt¶

This command programs the over voltage trip (OVT) set-point. If the input voltage exceeds the over voltage trip set-point for multiple samples, the input is disconnected and an OVT fault is indicated.

Address: 0x4030
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x4040
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.18. OverTripPwr¶

This command programs the over power trip (OPT) set-point. If the input power exceeds the over power trip set-point for multiple sample, the input is disconnected and an OPT fault is indicated.

Address: 0x4050
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x4060
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.19. UnderTripVolt¶

This command programs the under voltage trip (UVT) set-point. If the input voltage falls below the under voltage trip set-point for multiple samples, the input is disconnected and an UVT fault is indicated.

Address: 0x4070
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x4080
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.20. Slew Commands¶

10.8.21. RiseRampCurr¶

This command sets the current slew rate for increasing current transitions while in constant current regulation. MAXimum sets the slew to the fastest possible rate. MINimum sets the slew to the slowest rate. Slew rates less than the minimum value are set to MINimum. Slew rate settings less than the minimum value are set to MINimum. Slew rate settings greater than the maximum value are set to MAXimum.

Address: 0x5010
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 1 to MAXimum [A/ms] | MAXimum | MINimum
Data Format: 32-bit Floating Point Number
Query Address: 0x5020
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.22. RiseRampVolt¶

This command sets the voltage slew rate for increasing voltage transitions while in constant voltage regulation. The units for voltage slew rate are volts per millisecond. MAXimum sets the slew to the fastest possible rate. MINimum sets the slew to the slowest rate. Slew rates less than the minimum value are set to MINimum. Slew rate settings less than the minimum value are set to MINimum. Slew rate settings greater than the maximum value are set to MAXimum.

Address: 0x5030
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 1 to MAXimum [V/ms] | MAXimum | MINimum
Data Format: 32-bit Floating Point Number
Query Address: 0x5040
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.23. RiseRampPwr¶

This command sets the power slew rate for increasing power transitions while in constant power regulation. The units for power slew rate are watts per millisecond. MAXimum sets the slew to the fastest possible rate. MINimum sets the slew to the slowest rate. Slew rates less than the minimum value are set to MINimum. Slew rate settings less than the minimum value are set to MINimum. Slew rate settings greater than the maximum value are set to MAXimum.

Address: 0x5050
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 1 to MAXimum [W/ms] | MAXimum | MINimum
Data Format: 32-bit Floating Point Number
Query Address: 0x5060
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.24. RiseRampRes¶

This command sets the resistance slew rate for increasing resistance transitions while in constant resistance regulation. The units for resistance slew rate are ohms per millisecond. MAXimum sets the slew to the fastest possible rate. MINimum sets the slew to the slowest rate. Slew rates less than the minimum value are set to MINimum. Slew rate settings less than the minimum value are set to MINimum. Slew rate settings greater than the maximum value are set to MAXimum.

Address: 0x5070
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 1 to MAXimum [?/ms] | MAXimum | MINimum
Data Format: 32-bit Floating Point Number
Query Address: 0x5080
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.25. FallRampCurr¶

This command sets the current slew rate for decreasing current transitions while in constant current regulation. MAXimum sets the slew to the fastest possible rate. MINimum sets the slew to the slowest rate. Slew rates less than the minimum value are set to MINimum. Slew rate settings less than the minimum value are set to MINimum. Slew rate settings greater than the maximum value are set to MAXimum.

Address: 0x5090
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 1 to MAXimum [A/ms] | MAXimum | MINimum
Data Format: 32-bit Floating Point Number
Query Address: 0x50A0
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.26. FallRampVolt¶

This command sets the voltage slew rate for decreasing voltage transitions while in constant voltage regulation. The units for voltage slew rate are volts per millisecond. MAXimum sets the slew to the fastest possible rate. MINimum sets the slew to the slowest rate. Slew rates less than the minimum value are set to MINimum. Slew rate settings less than the minimum value are set to MINimum. Slew rate settings greater than the maximum value are set to MAXimum.

Address: 0x50B0
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 1 to MAXimum [V/ms] | MAXimum | MINimum
Data Format: 32-bit Floating Point Number
Query Address: 0x50C0
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.27. FallRampPwr¶

This command sets the power slew rate for decreasing power transitions while in constant power regulation. The units for power slew rate are watts per millisecond. MAXimum sets the slew to the fastest possible rate. MINimum sets the slew to the slowest rate. Slew rates less than the minimum value are set to MINimum. Slew rate settings less than the minimum value are set to MINimum. Slew rate settings greater than the maximum value are set to MAXimum.

Address: 0x50D0
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 1 to MAXimum [W/ms] | MAXimum | MINimum
Data Format: 32-bit Floating Point Number
Query Address: 0x50E0
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.28. FallRampRes¶

This command sets the resistance slew rate for decreasing resistance transitions while in constant resistance regulation. The units for resistance slew rate are ohms per millisecond. MAXimum sets the slew to the fastest possible rate. MINimum sets the slew to the slowest rate. Slew rates less than the minimum value are set to MINimum. Slew rate settings less than the minimum value are set to MINimum. Slew rate settings greater than the maximum value are set to MAXimum.

Address: 0x50F0
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 1 to MAXimum [?/ms] | MAXimum | MINimum
Data Format: 32-bit Floating Point Number
Query Address: 0x5100
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.29. Control Commands¶

10.8.30. PowerRange¶

This command activates a programmable series resistance and is available only in ARx and WRx models. When enabled, power dissipation is shared across series resistors and linear devices allowing the product to reach higher power levels.

Address: 0x6010
Function Code: 0x06
Access: Write
Register Count: 1
Parameters: 0 (low power) | 1 (high power)
Data Format: Boolean
Query Address: 0x6020
Function Code: 0x03
Access: Read
Register Count: 1
Data Format: 16-bit Integer

10.8.31. ControlMode¶

This command configures the MagnaLOAD electronic load’s control mode. Control Modes provides more information about the various options.

Address: 0x6030
Function Code: 0x06
Access: Write
Register Count: 1
Parameters: 1 (CURRENT) | 2 (VOLTAGE) | 3 (POWER) | 4 (RESISTANCE) | 5 (RHEOSTAT) | 6 (SHUNTREG)
Data Format: 16-bit Integer
Query Address: 0x6040
Function Code: 0x03
Access: Read
Register Count: 1
Data Format: 16-bit Integer

10.8.32. Function Generator Commands¶

10.8.33. FuncType¶

This command selects the desired function for the integrated function generator, which is active when the product’s set point source is set to function generator.

Address: 0x7010
Function Code: 0x06
Access: Write
Register Count: 1
Parameters: 0 (Sinusoid) | 1 (Square) | 2 (Step) | 3 (Ramp)
Data Format: 16-bit Integer
Query Address: 0x7020
Function Code: 0x03
Access: Read
Register Count: 1
Data Format: 16-bit Integer

10.8.34. FuncSinAmpl¶

This command sets the amplitude (Adc) for the sinusoid function when the set point source is set to 1 (function generator) and the function type is set to 0 (sinusoid).

Address: 0x7030
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x7040
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.35. FuncSinOff¶

This command sets the DC offset from zero (Adc) for the sinusoid function midline when the set point source is set to 1 (function generator) and the function type is set to 0 (sinusoid).

Address: 0x7050
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x7060
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.36. FuncSinPrd¶

This command sets the period (milliseconds) for the sinusoid function when the set point source is set to 1 (function generator) and the function type is set to 0 (sinusoid). The sinusoid’s period is the length of one full cycle.

Address: 0x7070
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 2 through MAX | MINimum (2 ms) | MAXimum (65,000 ms)
Data Format: 32-bit Floating Point Number
Query Address: 0x7080
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.37. FuncSquLoLevel¶

This command sets the low level amplitude for the square function when the set point source is set to 1 (function generator) and the function type is set to 1 (square).

Address: 0x7090
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x70A0
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.38. FuncSquHiLevel¶

This command sets the high level amplitude for the square function when the set point source is set to 1 (function generator) and the function type is set to 1 (square).

Address: 0x70B0
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x70C0
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.39. FuncSquLoPrd¶

This command sets the period/duration (milliseconds) that the square function remains at the low level amplituide when the set point source is set to 1 (function generator) and the function type is set to 1 (square).

Address: 0x70D0
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 2 through MAX | MINimum (2 ms) | MAXimum (65,000 ms)
Data Format: 32-bit Floating Point Number
Query Address: 0x70E0
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.40. FuncSquHiPrd¶

This command sets the period/duration (milliseconds) that the square function remains at the low level amplituide when the set point source is set to 1 (function generator) and the function type is set to 1 (square).

Address: 0x70F0
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 2 through MAX | MINimum (2 ms) | MAXimum (65,000 ms)
Data Format: 32-bit Floating Point Number
Query Address: 0x7100
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.41. FuncStepLoLevel¶

This command sets the low level amplitude for the step function when the set point source is set to 1 (function generator) and the function type is set to 2 (step).

Address: 0x7110
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x7120
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.42. FuncStepHiLevel¶

This command sets the high level amplitude for the step function when the set point source is set to 1 (function generator) and the function type is set to 2 (step).

Address: 0x7130
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x7140
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.43. FuncRampLoLevel¶

This command sets the low level amplitude for the ramp function when the set point source is set to 1 (function generator) and the function type is set to 3 (ramp).

Address: 0x7150
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x7160
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.44. FuncRampHiLevel¶

This command sets the high level amplitude for the ramp function when the set point source is set to 1 (function generator) and the function type is set to 3 (ramp).

Address: 0x7170
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 0 through MAX | MINimum | MAXimum
Data Format: 32-bit Floating Point Number
Query Address: 0x7180
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.45. FuncRampRisePrd¶

This command sets the period/duration (milliseconds) for the ramp function to transition from the low level amplitude to the high level amplitude when the set point source is set to 1 (function generator) and the function type is set to 3 (ramp).

Address: 0x7190
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 2 through MAX | MINimum (2 ms) | MAXimum (65,000 ms)
Data Format: 32-bit Floating Point Number
Query Address: 0x71A0
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.46. FuncRampFallPrd¶

This command sets the period/duration (milliseconds) for the ramp function to transition from the high level amplitude to the low level amplitude when the set point source is set to 1 (function generator) and the function type is set to 3 (ramp).

Address: 0x71B0
Function Code: 0x10
Access: Write
Register Count: 2
Parameters: 2 through MAX | MINimum (2 ms) | MAXimum (65,000 ms)
Data Format: 32-bit Floating Point Number
Query Address: 0x71C0
Function Code: 0x03
Access: Read
Register Count: 2
Data Format: 32-bit Floating Point Number

10.8.47. Configuration Commands¶

10.8.48. FactoryRestore¶

This command performs a factory restore to default EPROM values. Both Soft Restore and Hard Restore are available through command parameters.

Address: 0x8010
Function Code: 0x06
Access: Write
Register Count: 1
Parameters: 1 (Soft Restore) | 2 (Hard Restore)
Data Format: 16-bit Integer

10.8.49. Lock¶

This command configures the MagnaLOAD electronic load’s lock state. While locked, the stop button is the only functional button on the front panel. See Lock for more details on how lock works and how behaves relative to other locking inputs (front panel and digital input).

Address: 0x8030
Function Code: 0x06
Access: Write
Register Count: 1
Parameters: 0 (OFF) | 1 (ON)
Data Format: Boolean
Query Address: 0x8020
Function Code: 0x03
Access: Read
Register Count: 1
Data Format: 16-bit Integer

10.8.50. SenseMode¶

This command configures where the MagnaLOAD electronic load senses voltage. The sense location also effects how power and resistance are calculated. Local sensing monitors the directly across the output terminals. Remote sensing, as described in Remote Sense Connection, measures across the terminal JS2. This external connection can be used to improve regulation at the point of load, as is needed for example, in compensating voltage drops caused by wire resistance.

Address: 0x8060
Function Code: 0x06
Access: Write
Register Count: 1
Parameters: 0 (local) | 1 (remote)
Data Format: 16-bit Integer
Query Address: 0x8070
Function Code: 0x03
Access: Read
Register Count: 1
Data Format: 16-bit Integer

10.8.51. SetSource¶

The command selects and routes different set points sources to the digital controller. Operation of this feature is described in Set Point Source. By default, the source is set to local (value 0), where set points originating from the front panel or communication interfaces are routed to the ALx Series digital control. When the source is set to function generator (value 1), set points are generated internally, by a periodic function generator block. When external analog input (value 3) is set, the voltage(s) applied to the rear connector are converted into set points.

Address: 0x80A0
Function Code: 0x06
Access: Write
Register Count: 1
Parameters: 0 (local) | 1 (function generator) | 2 (external analog input)
Data Format: 16-bit Integer
Query Address: 0x80B0
Function Code: 0x03
Access: Read
Register Count: 1
Data Format: 16-bit Integer