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;
; date_verify loosely checks bcd date values to be in range in bin_date_time
;
date_verify: ;
assume ds:code,es:nothing
cmp byte ptr bin_date_time+0,20h ; century check
ja date_error ; jmp error
jz century_20 ; jmp in 20th century
cmp byte ptr bin_date_time+0,19h ; century check
jb date_error ; jmp error
cmp byte ptr bin_date_time+1,80h ; year check
jb date_error ; jmp error
century_20: ;
cmp byte ptr bin_date_time+1,99h ; year check
ja date_error ; jmp error
cmp byte ptr bin_date_time+2,12h ; month check
ja date_error ; jmp error
cmp byte ptr bin_date_time+2,00h ; month check
jbe date_error ; jmp error
cmp byte ptr bin_date_time+3,31h ; day check
ja date_error ; jmp error
cmp byte ptr bin_date_time+3,00h ; day check
jbe date_error ; jmp error
clc ; set success flag
ret ;
date_error: ;
stc ; set error flag
ret ;
;
; time_verify very loosely checks bcd date values to be in range in bin_date_time
;
time_verify:
assume ds:code,es:nothing
cmp byte ptr bin_date_time+0,24H
ja time_error
cmp byte ptr bin_date_time+1,59H
ja time_error
cmp byte ptr bin_date_time+2,59H
ja time_error
clc
ret
time_error:
stc
ret
;
; bcd_verify checks values in bin_date_time to be valid
; bcd numerals. carry set if any nibble out of range
;
bcd_verify: ;
assume ds:code,es:nothing
mov cx,4 ; 4 bytes to check
mov bx,offset bin_date_time ;
bv_loop: ;
mov al,[bx] ; get a bcd number (0..99)
mov ah,al ;
and ax,0f00fh ; 10's place in high ah, 1's in al
cmp al,10 ; is 1's place in range?
ja bv_error ; jmp out of range
shr ah,1 ; swap nibbles
shr ah,1 ; ...
shr ah,1 ; ...
shr ah,1 ; ...
and ah,0fh ; get rid of any erroneous bits
cmp ah,10 ; is 10's place in range
ja bv_error ; jmp out of range
inc bx ; next byte
dec cx ;
jnz bv_loop ;
clc ; set success flag
ret ;
bv_error: ;
stc ; set error flag
ret ;
;
; Dos 3.30 - The real time clock structures were moved to msbio2.asm
;
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