Intel C2518 FH8065501516710 Data Sheet

Intel

®

 Atom™ Processor C2000 Product Family for Microserver

September 2014

Datasheet, Vol. 2 of 3

Order Number: 330061-002US

535

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.

The Read-back command latches multiple counter outputs at one time. This single 

command is functionally equivalent to several counter latch commands, one for each 

counter latched. Each counter 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 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 are 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.

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 the unlatched count.