w65c134s Western Design Center, Inc., w65c134s Datasheet - Page 55

• Manufacturer Part Number: w65c134s
• Description: W65c134s 8-bit Microcontroller
• Manufacturer: Western Design Center, Inc.

5.2
Future versions of the W65C134S mask ROM may vary, but each version should contain standard machine
code that allows startup to an external memory. Standard versions of the W65C134S will always contain
such a startup option. Anyone writing a custom mask ROM for the 134 is encouraged to follow this
standard.
The startup standard allows a program in an external memory to be executed after RESET if the startup
code WDC (in ASCII, $57, $44, $43) is present at addresses $8000-$8002 or $0200-$0202. If the startup
code is found at either set of addresses, the mask ROM does a JMP instruction to $8004 or $0204
respectively. W65C134S chip selects CS6 and CS7 can be used to address the memories.
The startup standard was set (and will be followed) with the original WDC-101 mask ROM in the early
W65C134S prototypes.
W65C02S RESET vector ($FFFC) should be set to STARTUP.
STARTUP
;
TRY80
;
TRY02
;
NOEXT
External ROM Startup with W65C134S Mask ROMs
LDA
TSB
LDA
STA
LDA
CMP
BNE
LDA
CMP
BNE
LDA
CMP
BNE
JMP
LDA
CMP
BNE
LDA
CMP
BNE
LDA
CMP
BNE
JMP
JMP
#$01
BCR
#$C0
PCS3 ;ON P36, P37 (PCS3=$0007)
$8000 ;CHECK $8000 FOR 'WDC'
#'W'
TRY02
$8001
#'D'
TRY02
$8002
#'C'
TRY02
$8004 ;EXECUTE EXTERNAL ROM PROGRAM
$0200 ;CHECK $0200 FOR 'WDC'
#'W'
NOEXT
$0201
#'D'
NOEXT
$0202
#'C'
NOEXT
$0204 ;EXECUTE EXTERNAL ROM PROGRAM
MASK_ROM_PROGRAM
A sample startup program (modified from WDC-101) appears below.
;ENABLE EXTERNAL MEMORY BUS
;(BCR=$001B)
;ENABLE CHIP SELECTS CS6-, CS7-
;EXECUTE PROGRAM IN MASK ROM
The
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