Using the I/O-Bus Port
The 171 CBU 78090, 171 CBU 98090 and 171 CBU 98091 processors act as the I/O bus master for up to 32 I/O slave modules. The I/O modules on the bus can have addresses from 1 to 32. The I/O module connected to the processor I/O bus port has bus address number 1.
I/O-Bus Port Features
The I/O-Bus port includes the following features:
Feature |
Description |
|---|---|
Protocol |
Interbus |
Baud rate |
500 Kbits/s |
Media |
24 AWG, stranded (7x32), 3 twisted pairs, insulated cable with tinned copper (TC) conductors |
Connector type |
DB9 female |
Data integrity test |
CRC-16 |
Addressing |
Physical location |
Mode of operation |
Master–continuous shift register |
Topology |
Ring–extensible 1 level using a 170 BNO 6X1 XX branch interface module |
NOTE: On the transition from RUN to STOP states,
the processors apply the fallback setting to I/O modules –
on the local or the I/O-Bus – that support this feature.
I/O-Bus Port Diagnostics
Use the I/O LED on the processor to help diagnose the state of the processor.