Date   : Mon, 22 May 2006 21:33:31 +0200
From   : Eelco Huininga <eelco@...>
Subject: Re: 8271/1770 Opcodes

Hi Ian,

Actually they're not called opcodes, but commands :-)

The 8271 commands are:

Command  No of params  Description
&4A      2             Write sector
&4B      3             Write sectors
&4E      2             Write deleted sector
&4F      3             Write deleted sectors
&52      2             Read sector
&53      3             Read sectors
&56      2             Read deleted sectors
&57      3             Read deleted sectors
&5B      3             Read sector ID's
&5E      2             Verify sector
&5F      3             Verify sectors
&63      3             Format
&69      1             Seek
&6C      0             Read drive status
&7A      2             Write special registers
&7D      1             Read special registers

As you can see &7A is used to write a value to one of the 8271's special
registers. It is mostly used to write a value to the track register in copy
protection schemes.

Cheers,
Eelco



Ian Wolstenholme wrote:
> Is there a list of 8271 or 1770 opcodes anywhere?  The 8271 data
> sheet isn't much help especially if you are not fluent in binary without
> resorting to bits of paper and calculators and doing 1+2+4+8+16+32+64+128
> etc all over the place.
> 
> I'm trying to find out what opcode &7A does.
> 
> Best wishes,
> 
> 
> 
> Ian
>