User`s manual

Watlow Controls Communications Guide 15

Example (988 only):

Read register 0 (model number) of the controller at address 1.

Sent: 01 03 00 00 00 01 84 0A

Received: 01 03 02 03 DC B9 2D

Message: 988 (0x03DC).

Example (988 only):

Read register 1 and 2 (Process 1 and 2 values) of controller at

address 5.

Sent: 05 03 00 01 00 02 94 4F

Received: 05 03 04 00 64 00 C8 FF BA

Message: 100 (0x0064) and 200 (0x00C8).

Write to a Single Register Command (0x06)

This command writes a parameter to a single register. The controller will echo back

the command. An attempt to write to a read-only parameter returns an illegal data

address error (0x02). (See “Exception Responses,” pg. 4.9.)

controller address (one byte)

write to a register command (0x06)

data high byte

data low byte

CRC low byte

CRC high byte

Example (988 only): Set register 7 (SPI) to 200 (0x00C8) on controller at address 9.

Sent: 09 06 00 07 00 C8 38 D5

Received: 09 06 00 07 00 C8 38 D5

Write to Multiple Registers Command (0x10)

This command actually writes a parameter to only a single register. An attempt to

write to a read-only parameter returns an illegal data address error (0x02). (See

“Exception Responses,” pg. 4.9.)

Packet sent to controller:| nn | 10 | nn nn | 00 01 | 02 | nn nn | nn nn |

controller address (one byte)

write to multiple registers command (0x10)

starting register high byte

starting register low byte

number of registers to write high byte (0x00)

number of registers to write low byte (must be 0x01)

number of data bytes (must be 0x02)

data high byte

data low byte

CRC low byte

CRC high byte