Chapter 7
Understanding Discrete I/O
7-7
Time Constraints
COS detection requires real-time response from the host. At 230K baud,
there can be as little as 1.2ms between COS interrupts in a dynamic
system. These interrupts are not queued, so it is possible the host could
miss a COS interrupt if it is unable to meet the timing requirements. The
scanner firmware is able to detect whether the host is keeping pace with
COS interrupts and will set/clear the
cos_overrun
bit (bit 13) in
operating_status
in the dual port. See appendix A.
The host can enable the scanner to interrupt the host at the end of each
pass through the scan list. The host enables this mode by setting the
interrupt_after_each_scan
bit (bit 0) high in
config_data
in the dual port.
When the scanner reaches the end of the scan list, if this mode is enabled,
the scanner will set the
end_of_scan_list
bit (bit 0) high in
running_status
in
the dual port and will interrupt the host. The host must clear the
end_of_scan_list
bit.
This appendix
presents this information
A
dualport layout
B
example programs
C
KTx hardware registers
D
terminology
Interrupt at End of Scan List
What's Next