SN8P1600
8-bit micro-controller
CHECKSUM CALCULATION
The ROM addresses 0004H~0007H and last address are reserved area. User should avoid these addresses
(0004H~0007H and last address) when calculate the Checksum value.
ꢃ
Example:
The demo program shows how to avoid 0004H~0007H when calculated Checksum from 00H to the end of
user’s code
MOV
A,#END_USER_CODE$L
B0MOV
MOV
END_ADDR1,A
;save low end address to end_addr1
A,#END_USER_CODE$
M
B0MOV
CLR
END_ADDR2,A
;save middle end address to end_addr2
;set Y to ooH
Y
Z
CLR
;set Z to 00H
@@:
CALL
MOVC
B0BSET
ADD
YZ_CHECK
;call function of check yz value
;
FC
;clear C glag
DATA1,A
A,R
;add A to Data1
MOV
ADC
DATA2,A
END_CHECK
;add R to Data2
JMP
;check if the YZ address = the end of code
AAA:
INCMS
JMP
Z
;Z=Z+1
@B
;if Z!= 00H calculate to next address
;if Z=00H increase Y
JMP
Y_ADD_1
END_CHECK:
MOV
A,END_ADDR1
CMPRS
JMP
A,Z
;check if Z = low end address
AAA
;if Not jump to checksum calculate
MOV
A,END_ADDR2
A,Y
CMPRS
JMP
;if Yes, check if Y = middle end address
;if Not jump to checksum calculate
;if Yes checksum calculated is done.
;check if YZ=0004H
AAA
JMP
CHECKSUM_END
YZ_CHECK:
MOV
A,#04H
A,Z
CMPRS
RET
;check if Z=04H
;if Not return to checksum calculate
MOV
A,#00H
A,Y
CMPRS
RET
;if Yes, check if Y=00H
;if Not return to checksum calculate
;if Yes, increase 4 to Z
INCMS
INCMS
INCMS
INCMS
RET
Z
Z
Z
Z
;set YZ=0008H then return
;increase Y
Y_ADD_1:
INCMS
NOP
Y
JMP
@B
;jump to checksum calculate
CHECKSUM_END:
END_USER_CODE:
……….
……….
;Label of program end
SONiX TECHNOLOGY CO., LTD
Page 19
Revision 1.94
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