Honeywell I/O Scanner (for remote rack) 900S50-0360-00
Table 13 Expansion Rack Communication Status 
Status Possible Cause Controller Action What to do 
GOOD Comm port is functioning 
properly or comm port is 
not used 
N/A N/A 
DATA LINK 
FAILURE 
The communications to a 
particular rack is resulting 
in a lot of communication 
errors. 
1. Related rack monitor 
block’s RACK OK pin is 
turned off. 
2. Depending on the nature of 
the communication errors, the 
associated rack monitor 
block’s module diagnostics, 
and pins could be affected. 
3. Associated rack’s 
COMPORT DIAGNOSTIC is 
set to FAILED. 
4. Rack 1 COMPORT 
DIAGNOSTIC is set to 
FAILED. 
1. Use the OI to determine which 
rack is experiencing the comm 
errors. Verify that the expansion 
rack should be in the 
configuration 
2. Verify that the jumpers on the 
scanner are setup for the correct 
rack address. 
3. If a hub is used, check that all 
cables are properly connected to 
the hub, proper crossover cables 
are used, and that hub is 
powered. 
4. Cycle power to the rack. 
5. Cycle power to the hub. 
6. Replace the expansion rack’s 
power supply. 
7. Replace the expansion rack. 
8. Replace the expansion rack’s 
scanner board. 
9. Replace the main CPU. 
HARDWARE 
FAILURE 
The power-up test of the 
expansion rack Ethernet 
controller failed. 
1. All rack monitor block XIO 
PORT DIAG are set to 
HWFAIL and COMPORT 
DIAGNOSTIC is set to FAIL. 
2. All rack monitor block 
RACK OK pins are turned off. 
3. All modules in the 
configuration have their 
diagnostic set to 
MOD_NOCOMM, their rack 
monitor module fail pin is 
turned on., and the rack 
monitor block’s RACK OK pin 
is turned off. 
4. SYSTEM MONITOR 
block’s HW OK pin is turned 
off. 
5. The statuses for the AO, AI, 
DI, DO channels that are 
affected are set to 
BAD_CHANNEL.

Modbus Slave Devices 
This display gives you an overview of the individual Modbus or Modbus/TCP slave devices attached to the 
controller. Navigate to the desired device to see its status. 
Table 14 Modbus Slave Status 
Item Description 
Slave Name Name of slave device. 
Slave Address For Modus: 1-247 or 255. For Modbus/TCP: IP address. 
In Scan Current scan status of slave device. 
YES: The slave device is being scanned at its optimum rate. The scan rate is 
computed by the controller. 
NO: The slave device is being scanned at a reduced rate, or it is not being scanned 
at all. The possible reasons are: 
• SCAN ENABLED is set to NO. 
• COMM QUALITY is NONE or BAD. 
• the Modbus address of the slave device is set to 255. 
• the slave device is not defined in the controller configuration. 
• The RS-232 port protocol is not set to one of the Modbus Master protocols. 
Comm Quality NONE: This slave device is not defined in the controller configuration. 
GOOD: The slave device is being scanned at its optimum rate because its operation 
on the communications link is acceptable. 
BAD: The slave device is being scanned at a reduced rate because it has 
experienced an abnormal number of failed responses. Refer to the section 
“Troubleshooting a Comm Quality Problem” below. 
Messages Received The number of messages that were received and processed correctly since the last 
controller Cold Start. 
Data Link Errors The number of basic link-level errors generated by this slave since the last controller 
Cold Start. Refer to the section “Troubleshooting Data Link Errors” for more 
information. 
Application Errors The number of application errors generated by this slave since the last controller 
Cold Start. Application errors are messages that the slave device responded to with 
an exception code. For example, application errors can be caused by (a) writing to a 
read-only register, (b) accessing a register that is not supported by the slave device, 
or (c) using a Modbus function code that is not supported by the slave device. 
Scan Enabled YES: Scanning has been enabled 
NO: Scanning has been disabled