Intel
®
81341 and 81342—PMON Unit
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
952
Order Number: 315037-002US
18.4.2
Hardware Event Based Control
Hardware event based control allows a hardware event to control when another
command is executed. An example of this is controlling when a sample (snapshot) is
taken of the active counter(s). This is required to facilitate, among other things,
hardware
data queue analysis
. No command is executed until the command trigger
mux detects the event in the command trigger field of the command register. This
allows start, stop, sample, and other commands to be executed as a result of other
events happening.
Command Triggers
refers to the ability of a command to be issued to the
PMON
unit,
and have it not be executed until the desired event, as programmed when the pending
command was issued, is detected.
The
PMON
unit has no ability to queue commands so programming must be written so
as not to overwrite pending commands unless that is the desired effect.
For example, one could count how many memory reads happen before the first cache
hit occurs. This would be accomplished by programming the desired
PMON
counters to
start counting memory read events (Event A in
). Immediately
following that command the
PMON
controller is programmed to stop counting the
memory read events.