ADLINK ACL-8454/12 - Manual (Page 21)

Installation & Configurations • 13
2.8 Counters Architecture
There are at most four 8254 chips on the ACL-8454 card. The chip #1 (U1)
and chip #2 (U2) are default mounted on the card, therefore 6 counters are
default on board. It is possible to expand to four 8254 chips by plugging the
additional chip #3 (U3) and chip #4 (U4) into ACL-8454 and totally 12
counters are available. The default counters on chip #1 and #2 are labeled
as counter #1 to counter #6. The expandable counters on chip #3 and #4
are labeled as counter #7 to counter #12. Some counters are default
configured as independent counters and the others are default configured
as cascaded counters. Table 2.3 illustrates the relationship between the
reference number of chips and the counters number.
8254 Chip
Number
Reference
Number
Counter
Number Type of
Counter
Default
Installed
Counter #1 Independent
Chip #1 U1 Counter #2 Independent Installed
Counter #3 Independent
Counter #4 Independent
Chip #2 U2 Counter #5 Installed
Counter #6 Cascaded
Counter #7 Independent
Chip #3 U3 Counter #8 Independent Not installed
Counter #9 Independent
Counter #10 Independent
Chip #4 U4 Counter #11 Not Installed
Counter #12 Cascaded
Table 2.3 Default Counters Architecture