Rockwell Automation 1747-PCINT API Software for 1746 I/O - Manual (Page 12)

1–4 Overview
Publication 1747-6.5.3 June 1998
Your application (the code you develop using the API) uses the dual port memory
to communicate with the scanner to handle control functions on the 1746 backplane,
such as:
•
scanner commands and responses
•
battery and scanner status
•
scan rate frequency and timing
•
I/O image counters
•
priority messages and interrupts
•
semaphores to ensure data integrity
•
software-generated watchdogs
•
control of the 4 user-definable LEDs, the 2-position jumper, and the 3-
position switch
The scanner functionality of the dual port supports I/O control functions, such as:
•
synchronizing scans to the application
•
forcing I/O
•
defining discrete-input interrupts
•
defining I/O module-driven interrupts (such as for the 1746-BAS module)
•
enabling and disabling I/O slots
•
resetting I/O
In addition to providing access to the control scanner, the dual port memory also
provides non-volatile (optional battery-backed) storage for:
•
I/O values
•
application parameters (timers, counters, presets)
Scanner Modes
The scanner CPU operates in six basic modes:
•
performing POST (power-on self test)
•
waiting for host initialization
•
Idle
•
Scan
•
Faulted
•
non-recoverable fault
After the scanner successfully completes the POST, the scanner waits for an
initialization complete command from the application. Once the scanner receives
this command, the scanner enters Idle mode.
Before the scanner can enter Scan mode, the application must download a valid
I/O configuration to the scanner.
If a recoverable fault occurs, the scanner enters Faulted mode. Use the
OC_ClearFault API function to clear the fault before the scanner can resume
operating in Scan mode.