gnupic: gpasm numbers
Subject:
gpasm numbers
From:
pico ####@####.####
Date:
25 Aug 2004 00:32:04 +0100
Message-Id: <412BCFDA.5060306@sourceforge.net>
Additional note:
The most misleading thing about numbers in gpasm is that the default
radix is HEX and not DEC as in many other assembler.
Microchip application notes requires, especially the math related, that
the default radix is decimal.The same apply for third part code.
The gpasm manual don't explain that the default radix is hex in the
section related to numbers. Instead it's explained in the section
regarding command line arguments. As explained in the previous mail, some of
the numeric representations explained in the gpasm manual don't work.
One simple example:
#define KH *1000
#defime MH KH KH
; set processor speed
#define CLK 4000000
; or
#define CLK 4MH
; set timer0 prescaler
#define TM0PRE 16 ; set prescaler to 16 - minimum is 4
delay_ms:
; ARGS: 0-256 = W
; VARS: _tmp
; RET : W = 0
; NOTE: destroys the W register and set Z. C is untouched.
; timer0 must be started before enter this pice of code.
; otherwise this is a non returning call.
; DESC: delays 0-256 milliseconds
; HOOK: idle_1ms
#if CLK / TM0PRE / D'1000' > 0xff
#error "Prescaler in timer0 out of range"
#endif
movwf _tmp
skipnz
retlw 0
movlw ( CLK / 4 -4 ) / D'1000' / TM0PRE
movwf tmr0
call idle_1ms ; idle task called every ms in a time loop
movf tmr0
skipz
goto $-2
goto delay_ms+1
The result is a 3 or 4 time longer delay.
