Intel G1620T CM8063701448300 Manual De Usuario
Los códigos de productos
CM8063701448300
Datasheet
1221
PCU – iLB – 8254 Timers
26.3.2.2
Counter Latch Command
The Counter Latch command, written to Port 43h, latches the count of a specific
counter at the time the command is received. This command is used to ensure that the
count read from the counter is accurate, particularly when reading a two-byte count.
The count value is then read from each counter’s Count register as was programmed by
the Control register.
counter at the time the command is received. This command is used to ensure that the
count read from the counter is accurate, particularly when reading a two-byte count.
The count value is then read from each counter’s Count register as was programmed by
the Control register.
The count is held in the latch until it is read or the counter is reprogrammed. The count
is then unlatched. This allows reading the contents of the counters on the fly without
affecting counting in progress. Multiple Counter Latch Commands may be used to latch
more than one counter. Counter Latch commands do not affect the programmed mode
of the counter in any way.
is then unlatched. This allows reading the contents of the counters on the fly without
affecting counting in progress. Multiple Counter Latch Commands may be used to latch
more than one counter. Counter Latch commands do not affect the programmed mode
of the counter in any way.
If a counter is latched and then, some time later, latched again before the count is
read, the second Counter Latch command is ignored. The count read is the count at the
time the first Counter Latch command was issued.
read, the second Counter Latch command is ignored. The count read is the count at the
time the first Counter Latch command was issued.
26.3.2.3
Read Back Command
The Read Back command, written to Port 43h, latches the count value, programmed
mode, and current states of the OUT pin and Null Count flag of the selected counter or
counters. The value of the counter and its status may then be read by I/O access to the
counter address.
mode, and current states of the OUT pin and Null Count flag of the selected counter or
counters. The value of the counter and its status may then be read by I/O access to the
counter address.
The Read Back command may be used to latch multiple counter outputs at one time.
This single command is functionally equivalent to several counter latch commands, one
for each counter latched. Each counter's latched count is held until it is read or
reprogrammed. Once read, a counter is unlatched. The other counters remain latched
until they are read. If multiple count Read Back commands are issued to the same
counter without reading the count, all but the first are ignored.
This single command is functionally equivalent to several counter latch commands, one
for each counter latched. Each counter's latched count is held until it is read or
reprogrammed. Once read, a counter is unlatched. The other counters remain latched
until they are read. If multiple count Read Back commands are issued to the same
counter without reading the count, all but the first are ignored.
The Read Back command may additionally be used to latch status information of
selected counters. The status of a counter is accessed by a read from that counter's I/
O port address. If multiple counter status latch operations are performed without
reading the status, all but the first are ignored.
selected counters. The status of a counter is accessed by a read from that counter's I/
O port address. If multiple counter status latch operations are performed without
reading the status, all but the first are ignored.
Both count and status of the selected counters may be latched simultaneously. This is
functionally the same as issuing two consecutive, separate Read Back commands. If
multiple count and/or status Read Back commands are issued to the same counters
without any intervening reads, all but the first are ignored.
functionally the same as issuing two consecutive, separate Read Back commands. If
multiple count and/or status Read Back commands are issued to the same counters
without any intervening reads, all but the first are ignored.
If both count and status of a counter are latched, the first read operation from that
counter returns the latched status, regardless of which was latched first. The next one
or two reads, depending on whether the counter is programmed for one or two type
counts, returns the latched count. Subsequent reads return unlatched count.
counter returns the latched status, regardless of which was latched first. The next one
or two reads, depending on whether the counter is programmed for one or two type
counts, returns the latched count. Subsequent reads return unlatched count.