Datasheet

LPC Interface Bridge Registers (D31:F0)
266 Intel® Xeon® Processor D-1500 Product Family
Datasheet - Volume 1 of 4: Integrated Platform Controller Hub
March 2015
There are two special commands that can be issued to the counters through this
register, the Read Back Command and the Counter Latch Command. When these
commands are chosen, several bits within this register are redefined. These register
formats are described as follows:
RdBK_CMD—Read Back Command
The Read Back Command is used to determine the count value, programmed mode,
and current states of the OUT pin and Null count flag of the selected counter or
counters. Status and/or count may be latched in any or all of the counters by selecting
the counter during the register write. The count and status remain latched until read,
and further latch commands are ignored until the count is read. Both count and status
of the selected counters may be latched simultaneously by setting both bit 5 and bit 4
to 0. If both are latched, the first read operation from that counter returns the latched
status. The next one or two reads, depending on whether the counter is programmed
for one or two byte counts, returns the latched count. Subsequent reads return an
unlatched count.
3:1 Counter Mode Selection — WO. These bits select one of six possible modes of operation for the
selected counter.
0 Binary/BCD Countdown Select — WO.
0 = Binary countdown is used. The largest possible binary count is 2
16
1 = Binary coded decimal (BCD) count is used. The largest possible BCD count is 10
4
Bit Description
Bit Value Mode
000b Mode 0 Out signal on end of count (=0)
001b Mode 1 Hardware retriggerable one-shot
x10b Mode 2 Rate generator (divide by n counter)
x11b Mode 3 Square wave output
100b Mode 4 Software triggered strobe
101b Mode 5 Hardware triggered strobe
Bit Description
7:6 Read Back Command. Must be 11 to select the Read Back Command
5 Latch Count of Selected Counters.
0 = Current count value of the selected counters will be latched
1 = Current count will not be latched
4 Latch Status of Selected Counters.
0 = Status of the selected counters will be latched
1 = Status will not be latched
3 Counter 2 Select.
1 = Counter 2 count and/or status will be latched
2 Counter 1 Select.
1 = Counter 1 count and/or status will be latched
1 Counter 0 Select.
1 = Counter 0 count and/or status will be latched.
0 Reserved. Must be 0.