Technical Support Notes
| Article ID: | T1049 |
| Date: | 3/5/2001 |
| Product: | EPSON RC+ |
| Info: | I/O Timing |
Purpose
The purpose of this Technical Support Note is to describe
I/O timing on the EPSON RC+ system.
I/O Response for Drive Unit I/O and ISA
I/O
Drive
unit I/O and ISA I/O are both updated every 2 milliseconds by a hardware
interrupt generated by MIB board #1.
The table and figure below show the
typical response time.
| Item | Time | Description |
| Minimum Input Pulse Width | 2 ms | Minimum width of detected pulse. |
| Minimum Output Delay | 2 ms | Minimum time it takes to turn on an output. |
| Minimum Output Pulse Width | 2 ms | Minimum time that output must be turned on in the software. |
The following program was
run to generate the oscilloscope display above. Output bit 1 was
connected to input bit 1.
Do
Wait Sw(1) = On
On 1 :p>
Wait Sw(1) = Off
Off 1
Loop
Multi-tasking
When
running other tasks, the time for an output to turn on may be slightly longer,
depending on what the other tasks are doing. If one or more tasks are
executing only Do...Loop (no statements in between), the I/O response time will
be slower. This is worse case behaviour, but is not normal. If one
or more tasks are executing I/O or motion commands, then I/O response times are
generally not affected.
Traps
Trap Sw(xxx) timing is the same as with one simple task
using a Wait statement.
Ethernet I/O
All Ethernet I/O commands execute in
approximately 3 to 4 milliseconds. If the network is congested, commands
could take longer. In that case, you can add another Ethernet board that
is dedicated only to I/O. ENetIO_SwLatch can be used to latch
inputs to prevent them from being missed.
