Rockwell Automation 1771-IFF/A,D17716.5.116 FAST ANALOG INPUT MODULE - Manual (Page 50)

Module Programming
5-6
Publication 1771Ć6.5.116 - July 1996
The following description references the sequence numbers in
Figure 5.4.
Following a block transfer write “1” the module inhibits
communication until after it has configured the data “2,” performed
calibration check “3” (if requested), scanned the inputs “4,” and
filled the data buffer “5.” Write block transfers, therefore, should
only be performed when the module is being configured or
calibrated.
Any time after the second scan begins “6,” a BTR request “7” can be
acknowledged. This interrupts the scan and the BTR empties the
buffer. (If RTS is enabled, a BTR will only occur after the specified
time period. Refer to chapter 4.)
Following the BTR, the input module inhibits block transfer
communications with the programmable controller until it has
scanned its inputs “8” and new data is ready ”9.” The input module
repeats the scan sequence “10,” updating the input values until
another block transfer request is received. Therefore, BTRs will only
be completed as frequently as the total scan time of the input
module.
Figure 5.4
Block Transfer Time
1 2 3 4 5 6 7 8 9 10
Endof block
transfer write
1st
Scan
Module available to perform block transfer.
Block transfers are inhibiteduntil any
programmedRTS time has elapsed.
Note: Configure/Calibration time:
SingleĆended mode = 100ms configure; 1.5s calibration
Differential mode = 75ms configure; 750ms calibration
Scan time:
= 8ms for 16 singleĆended inputs (no scaling or digital filter);
= 4ms for 8 differential inputs (no scaling or digital filter) 12689
2nd
Scan
3rd
Scan
Block
Transfer
Write
time
Configure
time
Calibration
time
See note
In this chapter, you learned how to program your programmable
controller. You were given sample programs for your PLC-2, PLC-3
and PLC-5 family processors.
You also read about module scan time.
Chapter Summary