Intel C2518 FH8065501516710 Data Sheet

Intel

®

 Atom™ Processor C2000 Product Family for Microserver

Datasheet, Vol. 2 of 3

September 2014

534

Order Number: 330061-002US

It is often desirable to read the value of a counter without disturbing the count in 

progress. The three methods for reading the counters are as follows: a simple read 

operation, the Counter Latch command, and the Read-back command. They are 

explained below.

With the simple read and Counter Latch command methods, the count must be read 

according to the programmed format; specifically, if the counter is programmed for 

2-byte counts, 2 bytes must be read. The 2 bytes do not have to be read one right after 

the other. Read, write, or programming operations for other counters are inserted 

between them.

The first method is to perform a simple read operation. The counter is selected through 

port 40h (Counter 0), 41h (Counter 1), or 42h (Counter 2).

The Counter Latch command, written to port 43h, latches the count of a specific 

counter at the time the command is received. This command ensures that the count 

read from the counter is accurate, particularly when reading a 2-byte count. The count 

value is then read from each counter Count register that 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 and allows reading the contents of the counters quickly without 

affecting the counting in progress. Multiple counter latch commands are used to latch 

more than one counter. Counter latch commands do not affect the programmed mode 

of the counter in any way.

When a counter is latched and later latched again before the count is read, the second 

Counter Latch command is ignored. The first Counter Latch command issued is the first 

count read.