17 Apr
2006
17 Apr
'06
3:53 p.m.
On 4/17/2006 at 6:20 PM Dave Dunfield wrote:
By the time the Z80 was common, so were good assemblers
and
debuggers - but when the 8080 (ie: this instruction set) was designed,
there was no such software commonly available for "personal use" -
chances are your assembler was a pad of paper, a pencil and the Intel
databook (thats how I wrote my earliest software).
When I started to get into microprocessors, I wrote my own 8008
cross-assembler--and I used hex on a CDC 6600 (which was, curiously, an
octal machine--60 bit words with 6 bit characters). It just made sense. I
never finished the 8008 machine I was building, but went for the 8080 when
it came out as the MITS box. I revised the 8008 assembler to assemble
8080 codes. IIRC, my assembler was a one-pass job. There wasn't any good
reason to write a two-pass assembler, given the simplicity of the code I
was writing.
Hex actually made a lot of sense, not only from the standpoint of 8-bit
characters, but also due to the decimal arithmetic available on both the
8008 and 8080 MPU's. Try reading packed decimal coded in octal!
Cheers,
Chuck