Intel 386 User Manual Page 277

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Intel386™ EX EMBEDDED PROCESSOR USER’S MANUAL
10-34
With the readback command:
If both the status and counter values are latched, the user can read the value of the
Read/Write selection bits from the status register to know what bytes of the counter
value are being latched in the TMRn register.
If only the counter value is latched, you must know the Read/Write selection before the
counter value can be read correctly.
When a read-back command is issued to latch both the counter and the status of a timer, the
TMRn register holds both of these values. The first read of TMRn accesses the status byte
and the next one or two reads (depending on the R/W format) of TMRn access the timer’s
counter value.
10.4.1 Timer/Counter Unit Code Examples
The example code contains these software routines:
InitTimer Initializes the specified timers mode, counter value, inputs, and outputs
SetUp_ReadBack Configures the specified timer(s) for a read-back command
CounterLatch Latches the counter value of the specified timer
ReadCounter Performs a simple read command on the specified timers current counter
value
TimerISR Interrupt Service Routine for timer-generated interrupts
Code is also included that demonstrates how to change the timers counter value and issue a read-
back command. See Appendix C for included header files.
#include <conio.h>
#include “80386ex.h”
#include “ev386ex.h”
/*****************************************************************************
InitTimer:
Description:
This function initializes a timer’s inputs, outputs, operating mode,
and initial counter value.
Parameters:
Unit Unit number of the timer. The processor supports 0, 1 or 2
Mode Defines Counter Mode
Inputs Specifies Input sources
Output Specifies Which Output to drive
InitCount Value to be loaded into count register
Enable Enable (1) or disable (0) Timer
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