Datasheet

LPC Interface Bridge Registers (D31:F0)
Intel® Xeon® Processor D-1500 Product Family 267
Datasheet - Volume 1 of 4: Integrated Platform Controller Hub
March 2015
LTCH_CMD—Counter Latch Command
The Counter Latch Command latches the current count value. This command is used to
insure that the count read from the counter is accurate. The count value is then read
from each counter's count register through the Counter Ports Access Ports Register
(40h for counter 0, 41h for counter 1, and 42h for counter 2). The count must be read
according to the programmed format; that is, if the counter is programmed for two
byte counts, two bytes must be read. The two bytes do not have to be read one right
after the other (read, write, or programming operations for other counters may be
inserted between the reads). If a counter is latched once and then latched again before
the count is read, the second Counter Latch Command is ignored.
7.3.2 SBYTE_FMT—Interval Timer Status Byte Format Register
I/O Address: Counter 0 = 40h,
Counter 1 = 41h, Attribute: RO
Counter 2 = 42h Size: 8 bits per counter
Default Value: Bits[6:0] undefined, Bit 7=0
Each counter's status byte can be read following a Read Back Command. If latch status
is chosen (bit 4=0, Read Back Command) as a read back option for a given counter, the
next read from the counter's Counter Access Ports Register (40h for counter 0, 41h for
counter 1, and 42h for counter 2) returns the status byte. The status byte returns the
following:
Bit Description
7:6 Counter Selection. These bits select the counter for latching. If “11” is written, then the write is
interpreted as a read back command.
00 = Counter 0
01 = Counter 1
10 = Counter 2
5:4 Counter Latch Command.
00 = Selects the Counter Latch Command.
3:0 Reserved. Must be 0.
Bit Description
7 Counter OUT Pin State — RO.
0 = OUT pin of the counter is also a 0
1 = OUT pin of the counter is also a 1
6 Count Register Status — RO. This bit indicates when the last count written to the Count Register
(CR) has been loaded into the counting element (CE). The exact time this happens depends on the
counter mode, but until the count is loaded into the counting element (CE), the count value will be
incorrect.
0 = Count has been transferred from CR to CE and is available for reading.
1 = Null Count. Count has not been transferred from CR to CE and is not yet available for reading.
5:4 Read/Write Selection Status — RO. These reflect the read/write selection made through bits[5:4]
of the control register. The binary codes returned during the status read match the codes used to
program the counter read/write selection.
00 = Counter Latch Command
01 = Read/Write Least Significant Byte (LSB)
10 = Read/Write Most Significant Byte (MSB)
11 = Read/Write LSB then MSB