7 Jun
2002
7 Jun
'02
8:36 p.m.
Here's a page with some interesting "miscellaneous trivia" including the
transistor count, etc. of the 6800 ... I remember that came up as a question
some time back.
more regarding the 6502 below ...
Dick
<http://www.motorola.com/content/0,1037,121-286,00.html>
----- Original Message -----
From: "Pete Turnbull" <pete(a)dunnington.u-net.com>
To: <cctalk(a)classiccmp.org>
Sent: Friday, June 07, 2002 5:17 PM
Subject: Re: [CCTECH] Interesting tidbit on 6502
On Jun 7, 13:05, Richard Erlacher wrote:
I don't know that I have any of the NMOS 2 MHz 6502A parts any longer, but
I'm
planning a complete re-read of the undocumented opcodes and their behavior
sometime soon. I figure I can do it with a serial-port connected 805x family
part, with ports 1 and 2 monitoring the address lines, port 0 on the data bus,
and port 3 interacting with the clocks, R/W, sync, rdy, and irq lines. A fast
enough part can download the things it "sees" via the serial port and can hold
the circuit under test in WAIT until the data is uploaded to the host. A
timer can drive the Phase-0 clock. That should provide ample detail about
what, exactly happens on every opcode without a lot of fiddling with a logic
analyzer. It'll be a while, though ...
You may be confused about this. I don't know
of a single NMOS 6502 that
didn't adhere to the MOS-technology instruction set. There's no telling
whether that included the undocumented opcodes, but since Synertek and
Rockwell used the MOS mask set, I suspect there was no difference. The
later
Synertek parts may have been different since they
shrank the die and got
a bit
more speed, offering a 4 MHz 6502-C, which was an
NMOS part and worked
perfectly in NMOS-targeted systems that didn't work with the later CMOS
parts.
There certainly were differences between the sets of undocumneted opcodes
from different manufacturers of 2MHz 6502A parts. I remember one or two
"clever" bits of software that failed on some BBC Micros for that very
reason. Sean is absolutely right to avoid undocumented codes.
--
Pete Peter Turnbull
Network Manager
University of York