DESCRIPTION AND OPERATION
RIO CIRCUITRY
2 - 2
I-E96-317A
®
the bus clock is restarted. Since the link has been shut down,
the RMP has to be reconfigured by the MFP in order to restart.
2.
Remote Slave Processor
. At the remote end, the BFT is
used only for redundancy. If the active RSP module fails (no
bus clock), the BFT of the backup RSP expires after 1 millisec-
ond. This causes the backup RSP to become active and restart
the clock, preventing the slaves from shutting down.
Redundancy
Two completely independent RIO module sets, termination
units and serial links are used for redundancy. The MFP deter-
mines the primary (active) link. The primary link is started first
and then the backup link is downloaded. The backup link
remains in standby until the MFP commands it to take control.
A red LED, visible through the RIO front plate, is used to indi-
cate the active link. The RMP and all RSPs on the active link
will have their red LEDs turned on. The red LEDs of all RIO
modules on the standby link will be turned off.
A failover occurs when a RMP or RSP error is detected on the
primary link and no errors exist on the backup link. The two
RMPs must have unique expander bus addresses for the MFP
to manage both links independently. Each RSP pair must be
configured with the same serial link node address.
RIO CIRCUITRY
The RIO Module circuitry is comprised of the following seven
blocks (see Figure
1. Expander Bus Slave Interface
2. Expander Bus Master Interface
3. Shared RAM
4. Memory
5. CPU Support
6. Serial - CPU Interface
7. Serial Link Interface
An explanation of these blocks follows.
Expander Bus Slave Interface
This interface contains the circuitry necessary to provide com-
munication between the MFP and the RIO. A custom integrated
circuit enables the interface to recognize messages sent from
the MFP to the RIO across the Expander Bus.
