System status block (sys), Chapter 3 – Rockwell Automation 1771-SPI,D17716.5.122 SPI PROTOCOL INTERFACE User Manual
Page 26
Defining Command and Status Blocks
Chapter 3
3-4
The system status (SYS) block is returned by the SPI module on power-up
with the power up bit reset (to zero) to indicate that the module is ready for
a valid MCC. Until the SPI module is configured by a valid MCC, the
module returns the SYS with each BTR request regardless of the device
type or station address specified in the BTR request. Until the SPI module
stores a valid MCC, it returns the SYS with the following diagnostics to
help you correct data entry errors in the MCC:
a diagnostic code in word 3 (see 9000 series codes in chapter 6)
invalid device identification from the MCC polling queue list
– invalid device ID in SYS word 2, upper byte
– invalid device address in SYS word 4, lower byte
– invalid zone address (if used) in SYS word 4 upper byte
As soon as the SPI module receives a valid MCC, it returns the SYS with
the power-up bit set. Then, it will respond to BTR requests and poll
devices on the SPI network in the queue order established by the MCC.
Important: After you have successfully configured the SPI module with a
valid MCC, the use of the SYS is optional. If you want network status
returned by the SPI module as a result of polling devices in the SPI network
(one device-OK status bit per device), add the SYS block ID at the end of
the polling list of device IDs that you enter in the MCC. If using custom
command and status blocks such as CDB and CDS, you probably will have
little reason to use SYS after configuring the SPI module with a valid MCC.
Table 3.C
Bit/Word Map of System Status Block (SYS)
Word | Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
1
PU
Baud Select
AI
NF
DF
SYS Block ID
2
Device ID (returned for an invalid entry in MCC polling queue list)
Page Number
Total Pages
3
Diagnostic Word (returned for an Invalid MCC)
4
Zone Address for temperature control devices, only
(returned for an invalid entry in MCC polling queue list)
Device Address
(returned for an invalid entry in MCC polling queue list)
Communication Status Bits (OK Bits) for Devices on the SPI Network
5
Devices 32Ć47 indicated by word 5, bits 00Ć15 (1 bit per device)
6
Devices 48Ć63 indicated by word 6, bits 00Ć15 (1 bit per device)
: : :
18
Devices 240Ć255 indicated by word 18, bits 00Ć15 (1 bit per device)
System Status Block (SYS)