2 Mar
2011
2 Mar
'11
6:09 p.m.
On 2011 Mar 2, at 5:42 PM, Richard wrote:
In article <38a6c661425d97015d89cecf5ed5e293 at cs.ubc.ca>,
Brent Hilpert <hilpert at cs.ubc.ca> writes:
Fortune shines in a small way.
The MC146805E2 is a CMOS 6805 with no internal ROM. 8 pins are
multiplexed data and low order-address (A0-A7), another 5 pins are
higher-order-address (A8-A12). There are an address strobe pin and data
strobe pin for demuxing.
Other major features:
- 112 bytes internal RAM
- 16 programmable bidir IO port lines.
- internal 8-bit timer and 7-bit prescaler.
- on chip oscillator
I see there is only one accumulator in the 6805s, so - as Eric was
hinting at - the base CPU is paired down from the 6800. Haven't checked
whether it is op-code compatible.
I have here the 1984 Motorola "Single-Chip
Microcomputer Data" book,
which covers the 6805 family. There are a dozen or two variations of
the 6805. If you provide the full part number I can look it up.
Hopefully the image link I posted will help.
From an initial look at the the book however, it
appears most of the
variations are mask-programmed and I'm not seeing any opportunity to
address or substitute external ROM. There are some EPROM (68705,
windowed of course) and a couple of EEPROM (6805K2,3) variations.
It would be really helpful to know if these chips can be reprogrammed
at all. If not, they're headed for the recycle bin unless someone
here wants them.