RAMCTE01@ULKYVX.BITNET (06/29/87)
I am posting this for a friend who wants to tie into the cartridge slot
of a 512 ST. He is attempting to interface to a video digitizer (from
BYTE magazine - one of Steve Ciarcia's projects). Does anyone have
information on what needs to be done in hardware and software to
accomplish this?
Notes:
o Yes, I know the device in BYTE used a serial interface. He
has to do his I/O faster than that.
o I have seen articles/postings which talked about synthetic
writes to the cartridge port using reads to special addresses;
this approach isn't fast enough for what he wants to do.
o He plans on bringing the Read/Write line out from the processor
or wherever to the cartridge port.
This seems straightforward, but we've been told that a write to cartridge
memory space causes a bus error - hardly a desirable side effect. Is this
true, and can it be disabled in software?
Although there are perhaps more elegant ways of tying into the ST (DMA
port, etc.), he is pressed for time and needs a quick solution.
Please respond directly and I will post a summary, if anyone wants me to.
Thanks in advance,
Rick McTeague
Electrical Engineering Department
Speed Scientific School
University of Louisville
Louisville, KY 40292
BITNET address: RAMCTE01@ULKYVX.BITNETbraner@batcomputer.tn.cornell.edu (braner) (06/30/87)
[] I put a math chip (NS32081) on the cartridge port of my ST using the following hardware mod of the ST that I proposed as a standard: Cut pins 1, 39 and 40 behind the cartridge connector (they are redundant 5V and gnd pins). Connect pin 1 to the CPU R/W line. Build a decoder inside the ST (I used one chip, a 74HCT138) that passes the CPU ~AS signal but only when the address on the address bus is in the fourth megabyte ($3xxxxx). Connect that signal to pin 39. Connect pin 40 to the CPU clock (8 MHz). You can now write to the cart port using any address in the $3xxxxx range, and read using the original cartridge port addresses (only!). You can still use standard cartridges if you cut the traces to pins 1,39,40 inside them. - Moshe Braner
davel@hpvcla.HP.COM (David Lowe) (06/30/87)
>I am posting this for a friend who wants to tie into the cartridge slot >of a 512 ST. He is attempting to interface to a video digitizer (from >BYTE magazine - one of Steve Ciarcia's projects). Does anyone have >information on what needs to be done in hardware and software to >accomplish this? Steve Ciarcia's video digitizer/transmitter aritcles were in two issues of Byte. One of those issues also carried a hardware project for the ST. That ST article describes in detail a way to write to the cartridge port. Also included is a description of why running the R/W line out to the port won't work. (The project was a real time clock for the ST.) Speaking of real time clocks; is it feasible to provide battery backup to the keyboard controller? Thereby keeping it's clock running. Does GEMDOS set it's clock from the kyboard clock at Power-On/Reset? Dave Lowe hp-pcd!hpvcla!davel
jdg@elmgate.UUCP (Jeff Gortatowsky) (07/02/87)
In article <1567@batcomputer.tn.cornell.edu> braner@tcgould.tn.cornell.edu (braner) writes: >I put a math chip (NS32081) on the cartridge port of my ST using the >following hardware mod of the ST that I proposed as a standard: > [Lots of hardware talk I don't know about deleted here....8^) ] > >- Moshe Braner Excellent! Moshe how much would it cost me to get one just like it only with a 68881@12mhz???? (8^, <-- only half smiling, other half serious!). No software! I can handle that, I just need the hardware. I'll *settle* for 8mhz if that's easier. I have the chip, I just have no idea how to make a PC board. BTW I also have the 020 to go with the 881 but I guess that's too much too ask! 8^) Feel up to designing a new motherboard?!! 8^) -- Jeff Gortatowsky {seismo,allegra}!rochester!kodak!elmgate!jdg Eastman Kodak Company These comments are mine alone and not Eastman Kodak's. How's that for a simple and complete disclaimer?