Allen-Bradley 1747-SN User Manual page 164

Variable Variable Description
Time to perform M0 file write to enable
T
M0
BT
Scanner Output Delay time with BTs
present. There must be an output delay
time added for each BT buffer that is
T being used since the scanner processes
SNo–bt
only one BT enable or disable every
T (to minimize the impact on
SNo-bt
discrete I/O throughput).
Equals the sum of the throughput times
for all BTs scheduled to the same logical
rack (time waiting is queue), + T
T (time to schedule pending BT). If
btwait
multiple BTs are not being performed to
the same logical rack, this value equals
zero.
T RIO scan time without BTs
RIO
Amount that the RIO scan time can be
increased due to BTs. This includes the
T
btx
time for the scanner to initiate the BT
and transfer the data.
Time for the adapter to acknowledge the
BT request. For the 1747 ASB, the
manual defines this as no more than one
(ASB) backplane scan time and two RIO
T
adp–bt
scans. However, the two RIO scans are
already included in the above equation
so only the ASB scan time needs to be
added.
One processor scan time may occur
T before the SLC control program detects
ps
that the DN flag has been set or cleared
When calculating BT throughput, one T
RIO Scanner Output Delay Time (T
The tables provided in this section show the maximum scanner
output delay time (T
SNo
dependent on the following:
processor scan time, or time between immediate outputs (if no
BTs are present)
number of logical racks configured
whether normal or complementary I/O mode is selected
RIO baud rate (if complementary I/O is selected)
Specifications
SNo-bt
is also required to handle the BT response.
SNo-bt
) Tables
SNo
) for specific applications. T
Publication 1747 6.6 - July 1996
A–11
Location of Variable
appendix B
see the section Determining
T on page A-7
SNo-bt
calculated
see the section RIO Scan
Time Calculation (T ) on
RIO
page A-4
see the section Determining
T on page A-7
btx
adapter user manual
APS reference manual
is
SNo