kevinb@sdcsvax.ARPA (08/08/85)
I am new to the S-100 area, and having gotten an old IMSAI chassis with power
supply and motherboard, I am eager to make sure it's up to snuff before I
plug anything else into it. I am getting +11 on pins 1 & 51, +21 on 2, -21 on
52, 0 on the grounds (20,50,70,100) and about 2.3 or 4 everywhere else. Is this
normal? If not, a) is it within acceptability and b) if not, what kinds of
hints can you-all offer to help fix same? These values were tested WITHOUT
boards, and I only plan to put in 1-3 boards in for quite a while.
The name of the above is the PCS-80/15 microcomputer, using the EXP-10
motherboard, and the MBU-B 8085-based CPU. The motherboard also has traces
cut at the terminator at pins 71-74,75 being blank,76-78,79 being reconnected,
and 99. Also, the CPU board has spaghetti and cutouts around U31, a chip with
the label N82S31N 7734 and the label is an S. This chip isn't in the original
assembly instructions, which is ALL I have.
Anything of help on this, would also be a godsend.
I can do without the CPU, but I've got an Advanced Digital SUPER QUAD I can
drop into the motherboard, once it gets working.
Thanks in advance,
Kevin Belles
Kevin Belles - UUCP {ihnp4,cbosgd,sdcsvax,noscvax}!crash!kevinb
~~~~~ ~~~~~~ - ARPA crash!kevinb@{nosc,ucsd}GUBBINS@RADC-TOPS20.ARPA (Gern) (08/15/85)
For anyone doing ANY work with an S-100 system, especially if it is an older, possibly not IEEE-696 or even a new Z-100 which is IEEE-696, you MUST get a copy of the book by Sol Libes and Mark Garetz. I think the correct title is Interfacing to the IEEE-696/S-100 Bus. It is very well written and will describe everything you need to know. It helps if you have a copy of the standard: IEEE Standard 696 Interface Devices ANSI/IEEE Std 696-1983 It is Heathkit part number 500-69 A rough draft of the standard was published July 1979 in Computer (IEEE) magazine. The standard says the +8 lines (pins 1 & 51) must have an instantaneous minium greater than +7V, instant max less than 25V and an average max less than +11V. The pin 2 is 14.5<16<35V with average <21.5 Pin 52 is the same, but negative. As far as signals go, high state is +2V or greater on the reciever end. If you have an old S-100 system, therer are about 4 lines that have have been changed, but they were never used much anyhow (Memory write lock, etc.). Major concern is the bus termination circuits to prevent ringing and such. I am doing a lot of work at home, on the side on a 6 channel stereo sound/speech Synthesizer/joysticks (both analog and digital types)/ clock-calendar with battery backup and on-chip-leap-year. The design is finalized and I am workin on the PC Board layout. It is completely IEEE-696/S-100. So if you have any S-100 questions, I'll take a stab at them. Cheers, Gern -------