Converting ASCII to Hex (was: 1st stage loader for IMSAI - need ascii to binary conversion)
25 Feb
2008
25 Feb
'08
2:44 p.m.
Really this is pretty easy (this does NO error checking, and only accepts upper
case characters):
int hex (char ascii)
{
int value;
value = ascii - '0';
if (value > 9)
value += '0' - 'A' + 0x0A;
return value;
}
Improvements are left as an exercise for the reader/student.
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25 Feb
25 Feb
5:11 p.m.
On 25 Feb 2008 at 14:44, Tom Watson wrote:
Really this is pretty easy (this does NO error
checking, and only accepts upper
case characters):
Okay, being a dumb ol' bit-twiddler, I couldn't resist:
(input character in A)
adi 0c0h
mov b,a
sbb a
ani 09h
add b
ani 0fh
Okay, folks--anyone got a shorter sans-jump one? One that perhaps
doesn't require an extra register? How about one that uses a DAA to
do something sneaky?
Cheers,
Chuck
7:29 p.m.
New subject: Converting ASCII to Hex (was: 1st stage loader for IMSAI - need ascii to binary conversion)
Chuck Guzis wrote:
Okay, folks--anyone got a shorter sans-jump one? One
that perhaps
doesn't require an extra register? How about one that uses a DAA to
do something sneaky?
Although it's the other way round, this is one of my top five favorite
gems of all time:
; input:
; al = single hex digit
;
; output:
; al = single ASCII digit
;
; destroys:
; flags
;
cmp al,10 ; if x < 10, set CF = 1
sbb al,69h ; 0-9: 96h .. 9Fh, A-F: A1h..A6h
das ; 0-9: subtr. 66h -> 30h-39h,
; A-F: subtr. 60h -> 41h..46h
Using the above as a basis for ascii-to-hex is left as an exercise for
Chuc^H^H^H^Hthe reader.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
7:53 p.m.
On 25 Feb 2008 at 21:29, Jim Leonard wrote:
Although it's the other way round, this is one of
my top five favorite
gems of all time:
Yeah, Jim, but we were talking 8080 code here. Heck, if we extend
the problem to the x86 family, then the original problem solves in 3
instructions as:
(al) = input character ('0'-'9', 'A'-'F')
(al) = on exit, 00h-0fh
sub al,030h
db 0d4h,010h ; funny aam
db 0d5h,009h ; funny aad
(not fast, but short)
But let's go back to the OP and his 8080 problem...
Cheers,
Chuck
10:22 p.m.
New subject: Converting ASCII to Hex
Chuck Guzis wrote:
Yeah, Jim, but we were talking 8080 code here.
I know; I just get tired of all the 808x bashing sometimes. Had to
represent! ;-)
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
9:01 p.m.
New subject: Converting ASCII to Hex
Chuck Guzis wrote:
On 25 Feb 2008 at 14:44, Tom Watson wrote:
Is it 8008 compatable code? :)
Really this is pretty easy (this does NO error
checking, and only accepts upper
case characters):
Okay, being a dumb ol' bit-twiddler, I couldn't resist:
(input character in A)
adi 0c0h
mov b,a
sbb a
ani 09h
add b
ani 0fh
Okay, folks--anyone got a shorter sans-jump one? One that perhaps
doesn't require an extra register? How about one that uses a DAA to
do something sneaky? Cheers,
Chuck
9:19 p.m.
New subject: Converting ASCII to Hex
On 25 Feb 2008 at 22:01, woodelf wrote:
Is it 8008 compatable code? :)
Well, yes, it is, as a matter of fact. If you use the "new"
instruction mnemonics, you don't have to change a thing:
adi 0c0h
mov b,a
sbb a
ani 09h
add b
ani 0fh
If you have the "old" style assembler, you might need to change a few
mnemonics; e.g. ani = ndi, mov b,a = lba, sbb a = sba, add b = adb
Cheers,
Chuck
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6 comments
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