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C–– Efficiency
5-43Code Development Tools
Mainasm.asm contains the most complex assembly. It is responsible for
initializing assembly variables, enabling or disabling interrupts, and setting up
any timers or I/O ports. It also enables the interrupts. The part that is important
to the project, _goasm, is called at the beginning of the C–– main routine.
;****************************************************************
; Main program
;
; Set i/o for any peripherals (eg ADC chip, flash card or LCD)
; and initialize variables as necessary. All user code should
; start here.
;****************************************************************
; clear the seconds passed counter
zac a0
mov *seconds_passed,a0
; Set TIMER2 to run from the RTO/CTO (32 kHz) and with a 1000ms period. Set this
by
; loading TIM2 with (32768 x 1000/1000), minus 1.
in a0,IntGenCtrl
or a0,TIM2REFOSC ;set bit 9, CTO clock (32 kHz)
and a0,~TIM2ENABLE ;clear bit 11, TIM2 enable
out IntGenCtrl,a0
mov a0,32768 – 1 ;setup a 250ms period
out TIM2,a0 ;load TIM2 and PRD2 in one step
in a0,IntGenCtrl
or a0,TIM2IMR + TIM2ENABLE ;set bit 2 (TIM2 interrupt
;enable) and bit 11
out IntGenCtrl,a0
inte
ret
In this example, it clears seconds_passed, which was used in the first file
(timer2_isr.asm), sets up timer2 to run at a 1Hz interval, and enables the
interrupts.
The fifth important file is cmm1.asm. This file is responsible for supporting C––
to assembly function calls. It takes parameters passed on the stack, processes
them, and returns a 16-bit value in A0. In C–– the 16-bit return value is always
of type int.
;****************************************************************
; CMM1.ASM
;
; Revision 1.00
;****************************************************************
rorg 0x0
global _getSecondsPassed
include ”ram\ram.irx”
; retrieve the seconds that have passed, and reset the counter
_getSecondsPassed
rpt2–2 ; interrupt can still fire for 2 cycles
intd ; leaving these out can cause loss of a second
mov a0~, *seconds_passed
zac a0