Rockwell Automation 1771-SPI,D17716.5.122 SPI PROTOCOL INTERFACE - Manual (Page 50)

Creating Command and Status Blocks
Chapter 4
4-14
The SPI module receives status from the target device and returns Custom
Data Status (CDS) to the PLC processor whenever the target device:
receives the Custom Data Block (CDB) from the SPI module
is polled by the SPI module
The contents of the CDS are different for each condition:
For this origin: CDS contains
CDB command the reflected commandĆcode pairs that you entered in CCB
polling numeric values (status bits and process variables)
specified by the commandĆcode pairs and located in their addresses
The size is the same for both conditions and is equal to the sum of:
four header words
number of command-code pairs for status that you entered in CCB
If the SPI module detects a fault, it returns the CDS with only the first
three words containing fault diagnostics:
words 1 and 2 identify the target device having the fault
word 3 contains the 70xy series error codes described in chapter 6.
We identify fault diagnostic information in bold print.
CDS Bit/Word Map
Word 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
1 0 CR CE 0 DC Device ID
2 Zone Address (if used) Device Address
3 If the SPI module detects a fault, it sets an error code (70xy series) to help identify the cause of the fault
4 0 0 0 0
starting at 5,
up to 64
If no communication fault:
If origin is a CDB, CDS reflects all the commandĆcode pairs that you entered in CCB.
If origin is polling, CDS returns numeric values specified by the commandĆcode pairs.
If SPI detects a communication fault, it
clears all status words starting at word 4, and returns words 1Ć3 with a diagnostic code (70xy) in word 3.
Custom Data Status, CDS, to
Return Device Status From
the SPI Module