gnupic: stumped with simple led/button circuit
Subject:
stumped with simple led/button circuit
From:
Tsu Do Nimh ####@####.####
Date:
28 Feb 2005 22:08:20 +0000
Message-Id: <cd4a1628050228140723f6fce2@mail.gmail.com>
Hi,
My first time posting.
I have, to test my setup, put together a simple circuit w/p16f877a,
20MHz crystal, button on PORTA,0, and led on PORTB,0. I've compiled
assembler code to this target that copies the PORTA input register
(button) to the PORTB output register.
I checked all the voltages and connections, tried (success) shorting
the led cathode to ground. I attached an oscilloscope lead to the
crystal to verify it is ticking ok.
But the button doesn't work. After looking at the hardware, I assume
the problem is somewhere in the programming of the chip.
I'm using a PS+ and the picp programmer to load the program.
Disassembling the .hex file results in:
=8<-------
000000: 1406 bsf 0x6, 0
000001: 1683 bsf 0x3, 0x5
000002: 1006 bcf 0x6, 0
000003: 1283 bcf 0x3, 0x5
000004: 0805 movf 0x5, w
000005: 0086 movwf 0x6
000006: 2804 goto 0x4
002007: 3f32 addlw 0x32
=8<-------
After loading the corresponding .hex code (gen'td using 'gpasm -o
ledon.hex ledon.asm'), and disassembling a dump from the chip using
picp/gpdasm, the code looks like:
=8<-------
000000: 0000 nop
000001: 1402 bsf 0x2, 0
000002: 1002 bcf 0x2, 0
000003: 1002 bcf 0x2, 0
000004: 0001 dw 0x1 ;unknown opcode
000005: 0004 dw 0x4 ;unknown opcode
000006: 0086 movwf 0x6
000007: 2805 goto 0x5
=8<-------
Can anyone provide insight as to why I'm getting this different code
out, or how I might look somewhere else for the source of the problem?
Thanks for your help, in advance.
Yours,
Tsu Do Nimh
