Watlow Series 988 Family - Manual (Page 26)

4.8 Data Communications with the Watlow Series 988 Family Sending Commands, Chapter 4
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
Packet returned by controller: | nn | 10 | nn nn | 00 01 | 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)
CRC low byte
CRC high byte
Loop Back Command (0x08)
This command simply echoes the message. This serves as a quick way to check
your wiring.
Packet sent to controller:| nn | 08 | nn nn | nn nn |
∆ ∆ ∆ ∆ ∆ ∆
controller address (one byte)
loop back command (0x08)
data high byte
data low byte
CRC low byte
CRC high byte
Example: Run loop back test on controller at address 40 (0x28).
Sent:
28 08 55 66 77 88 31 B7
Received: 28 08 55 66 77 88 31 B7
NOTE:
Because the read
command can only
read 32 registers,
the high byte for
the number of
registers will
always be 0.
Modbus RTU