Piclisters,

Pardon me but just when I thought I
had a handle on page jumping in the
16C57, it springs
a new surprise.

OK, here's a programme to test
CBLOCK instruction. There's a whole
lot of dummy registers
defined and the programme just goes
thru and clears each of them. It
jumps to the reset
address on PAGE #3 'cause I'd like
to fit some routines outside of
PAGE #0 for once.
(I've got a real programme to write
that calls for a lot of registers.)



The programme compiles OK but MPLAB
says there's a problem with some
registers and their page
assignments :-
---------------------------------
Compiling CALLER2.ASM:
Command line:
"C:\PROGRA~1\MPLAB\MPASMWIN.EXE
/dDEBUG /e+ /l+ /x- /w0 /c+ /m+
/rhex /p16C57 /q A:\CALLER2.ASM"
Warning[216] A:\CALLER2.ASM 21 :
Radix superceded by command line.
Message[308] A:\CALLER2.ASM 22 :
Warning level superceded by command
line value. (0)
Message[306] A:\CALLER2.ASM 109 :
Crossing page boundary -- ensure
page bits are set.
Message[302] A:\CALLER2.ASM 141 :
Register in operand not in bank 0.
Message[302] A:\CALLER2.ASM 142 :
Register in operand not in bank 0.
Message[302] A:\CALLER2.ASM 143 :
Register in operand not in bank 0.
Message[302] A:\CALLER2.ASM 144 :
Register in operand not in bank 0.
Message[302] A:\CALLER2.ASM 145 :
Register in operand not in bank 0.
Message[302] A:\CALLER2.ASM 146 :
Register in operand not in bank 0.
Message[302] A:\CALLER2.ASM 147 :
Register in operand not in bank 0.
Message[302] A:\CALLER2.ASM 148 :
Register in operand not in bank 0.
Message[306] A:\CALLER2.ASM 187 :
Crossing page boundary -- ensure
page bits are set.

Build completed successfully.
---------------------------------

When we step the programme thru, it
finds its way to PAGE #3 then back
to PAGE #0 and
into the CLEAR routine, just like
it should.

BUT, when we step thru CLEAR,
clearing registers as we go, it
gets up to reg1A, then PCL
resets and we finish up back near
the start someplace.

OK, I thought the 57's general
purpose registers go from 0x08 up
to 0x07F and so we should be able
to
handle the registers assigned to
it. What's going on?

Advice much appreciated!

Thnax in advance - PJH



;*****************************************************************

;Here be ye programme ========>


 title  caller2
;DATE     : June 25, 1999
;PURPOSE  : to figure out how
CBLOCKS work!!!!

 list p=16C57, F=inhx8m, R=hex
 errorlevel 0,-305
 include "A:\p16c5x.inc"
 __CONFIG _CP_OFF &_WDT_OFF
&_XT_OSC

;**********************************************************************

;MACRO SECTION ... 'page select'
MACROS
; PA0 = 0X05
; PA1 = 0X06
; PA1    PA0
;   0      0      Page #0
(0000-01FF)
;   0      1      Page #1
(0200-03FF)
;   1      0      Page #2
(0400-04FF)
;   1      1      Page #3
(0600-07FF)
;**********************************************************************

Page_0 MACRO
 bcf   STATUS,5
 bcf   STATUS,6
 ENDM

Page_1 MACRO
 bsf   STATUS,5
 bcf   STATUS,6
 ENDM

Page_2 MACRO
 bcf   STATUS,5
 bsf   STATUS,6
 ENDM

Page_3 MACRO
 bsf   STATUS,5
 bsf   STATUS,6
 ENDM

;**********************************************************************

;VECTOR ASSIGNMENTS
;**********************************************************************

_16C57_4 equ 0x07FB    ;Don't go
over END-OF_PAGE with RESET
instructions.

;**********************************************************************

;REGISTER ASSIGNMENTS
;**********************************************************************

 CBLOCK 0x08
reg0
reg1
reg2
reg3
reg4
reg5
reg6
reg7
reg8
reg9
regA
regB
regC
regD
regE
regF
reg10
reg11
reg12
reg13
reg14
reg15
reg16
reg17
reg18
reg19
reg1A
reg1B
reg1C
reg1D
reg1E
reg1F
 ENDC

;*******************************************************************************
*******

;PAGE #0
;START the MAIN PROGRAMME  at 0x00
and jump to reset address.
Subroutines are placed in
;lower half of Page #0, ie 00-0FF.
Main programme starts at 0100. LCD
message routines
;go in PAGE #1. Eventually.
;*******************************************************************************
*******

        org      0x00

go_rst  nop
        Page_3
        goto     reset

start   clrf     FSR
        goto     main

;************************************************************

;CLEAR ... initialises registers to
start up values
;************************************************************

clear   clrf     reg0
        clrf     reg1
        clrf     reg2
        clrf     reg3
        clrf     reg4
        clrf     reg5
        clrf     reg6
        clrf     reg7
        clrf     reg8
        clrf     reg9
        clrf     regA
        clrf     regB
        clrf     regC
        clrf     regD
        clrf     regE
        clrf     regF
        clrf     reg10
        clrf     reg11
        clrf     reg12
        clrf     reg13
        clrf     reg14
        clrf     reg15
        clrf     reg16
        clrf     reg17
        clrf     reg18
        clrf     reg19
        clrf     reg1A
        clrf     reg1B
        clrf     reg1C
        clrf     reg1D
        clrf     reg1E
        clrf     reg1F
        retlw    0x00

;**************************************************************

;Beginning of main programme from
the the upper half of PAGE #0
;**************************************************************

        org      0x0100

main    call     clear

look    nop

        goto     look

;****************************************************************************

;PAGE #1
;****************************************************************************

        org      0x0200

;****************************************************************************

;PAGE #2
;****************************************************************************

        org      0x0400



;****************************************************************************

;PAGE #3
;THE HOME OF THE RESET VECTOR
;****************************************************************************

        org      0x0600

        org      0x0700
;Upper half of the page

        org      _16C57_4
;RESET vector at the end of Page #1

reset   nop
        Page_0
        goto     start
        end


--