Re: 1802 vs 1805/6

Lee Hart

On 6/26/2010 2:14 AM, Magnus wrote:

I was looking for cheap (surplus) components at small components shop here in Sweden when I spotted lots of COSMAC chips in the list. OF COURSE there was the 1802, which I just bought on eBay ...but also 1805/6. The latter has some extra functions like internal timers/counters and extra instruxctions.
My question is, is there any idea to grab an 1805/06 instead of the 1802 "just in case ..." or will the original 1802 do most (all) work brilliant w/o the extra frills and laces?

I'd be hoping to grab some latches/decoders and buffers as well as IC sockets for wiring, something I cannot find just like that here in Sweden any longer.
The 1804/5/6 are slightly improved versions of the 1802. Depending on the particular model, they have internal ROM, RAM, a timer, and some new instructions. They were intended for single-chip microcontroller applications, where you ordered them with your program already in the internal ROM.

Not much code was written to use the new instructions. The internal ROM is useless for general purpose applications; it is typically disabled so you can use it with external memory chips instead.

The only thing missing in the 1804/5/6 that the 1802 has is the LOAD mode. Unfortunately, LOAD is used in the Elf computers for their front panel interface.

I bought some 1805's on eBay for a good price. If you'd like to experiment, I'd be happy to swap one for an 1802.
Lee A. Hart | Ring the bells that still can ring
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