Intel C2518 FH8065501516710 Data Sheet

Intel

®

 Atom™ Processor C2000 Product Family for Microserver

September 2014

Datasheet, Vol. 2 of 3

Order Number: 330061-002US

533

The counter/timers are programmed in the following fashion:

1. Write a control word to select a counter.
2. Write an initial count for that counter.
3. Load the least and/or most significant bytes (as required by control word bits 5, 4) 

of the 16-bit counter.

4. Repeat with the other counters.

Only two conventions need to be observed when programming the counters. First, for 

each counter, the control word must be written before the initial count is written. 

Second, the initial count must follow the count format specified in the control word 

(least significant byte only, most significant byte only, or least significant byte and then 

most significant byte).

A new initial count is written to a counter at any time without affecting the counter 

programmed mode. Counting is affected as described in the mode definitions. The new 

count must follow the programmed count format.

If a counter is programmed to read/write 2-byte counts, the precaution applies as 

follows: a program must not transfer control between writing the first and second byte 

to another routine which also writes into that same counter. Otherwise, the counter is 

loaded with an incorrect count.

The Control Word Register at port 43h controls the operation of all three counters. 

Several commands are available as follows:

• Control Word command - Specifies which counter to read or write, the operating 

mode, and the count format (binary or binary-coded decimal). 

• Counter Latch command - Latches the current count so the system reads it. The 

countdown process continues. 

• Read Back command - Reads the count value, programmed mode, the current state 

of the OUT pins, and the state of the null count flag of the selected counter.

 lists the six operating modes for the interval counters.

0

Out signal on end of count (=0)

Output is 0. When the count goes to 0, the output goes to 1 

and stays at 1 until the counter is reprogrammed.

1

Hardware-retriggerable one-shot

Output is 0. When the count goes to 0, the output goes to 1 

for one clock time.

2

Rate generator (divide by n counter) Output is 1. The output goes to 0 for one clock time, then 

back to 1 and the counter is reloaded.

3

Square  wave  output

Output is 1. The output goes to 0 when the counter rolls over, 

and the counter is reloaded. The output goes to 1 when the 

counter rolls over, and the counter is reloaded, etc.

4

Software triggered strobe

Output is 1. The output goes to 0 when the count expires for 

one clock time.

5

Hardware triggered strobe

Output is 1. The output goes to 0 when the count expires for 

one clock time.