Micromod Micro-DCI: 53MC5000 PLC AND PRINTER INTERFACES - Manual (Page 73)

Table 6-3. Control and Status Bytes for PCS Modbus Master
Title Definition DDI-A DDI-B Set
By
De-
fault
Setup
Error It indicates the following: 0 = No Error, 1 = L-bytes to
read > 64, 2 = C-words to read > 64, 3 = L-bytes to write
> 64, 4 = C-words to write > 64, 5 = Invalid Function
Code, 6 = Write command 6 specifies more than 1 word
of L or C data, 10 = Scan Time at 0. These error codes
cause DDI channel operation to halt. B684 B660 Soft-
ware 0
Scan
Time It is the PCS time period for the read and write phases
of a PCS-PLC transaction. It is entered as a number
from 1 to 255 which represents 100 to 25,500 ms. (See
Section 3.7.) B685 B661 User 0
Scan
Overruns
Counter* This counter is incremented each time the read-write
phases exceed the specified Scan Time. It indicates the
Scan Time should be increased. (See Section 3.7.) B686 B662 Soft-
ware 0
*User can reset by writing zeros into the datapoints.
Table 6-4. Read Control Bytes for PCS Modbus Master
Title Definition DDI-A DDI-B Set
By
De-
fault
PLC Address It is the address of the PLC to be accessed. B664 B640 User 0
Starting PLC Memory
Address (Low) The two byte PLC memory starting address.
Each byte is a decimal number; however,
both bytes together function as a 16 bit
unsigned binary integer, e.g., the PLC
hexadecimal address 4180
16
would be
entered as 65
10
in the high byte B666 [or
B642] and 128
10
in the low byte B665 [or
B641]. (See Appendix A for decimal
conversions.)
B665 B641 User 0
Starting PLC Memory
Address (High) B666 B642 User 0
Number of L-Bytes to
Read The number of L-bytes that are to be
accessed from the PLC. B667 B643 User 0
Number of C-Words
to Read The number of C-words that are to be
accessed from the PLC. B668 B644 User 0
Function Code It is the read command function code as
follows:
1 = Read Output Status (L)
2 = Read Input Status (L)
3 = Read Holding Registers (C - PLC
registers may contain L-values.)
4 = Read Input Registers (C - PLC
registers may contain L-values.) B669 B645 User 0
1 of 2
Section 6. MODBUS RTU Mode
MODBUS2
6-9