cheesestraws
Well-known member
Very nifty! 
Apple Communications Slot technical documentation?
- Thread starter David Cook
- Start date
Trash80toHP_Mini
NIGHT STALKER
VERY, very cool! Cant wait to see how your work on this progresses.
Sorry I broke in with that PCI CSII machine info, didn't track that you were specifically targeting the CS1 era PPC machines with 630 PDS from the NuBus Architecture generation. Should be very interesting info coming up indeed.
Do you have any plans for a future passthru connector to explore expanded use of the Networking capability of the CS1 Slot?
Sorry I broke in with that PCI CSII machine info, didn't track that you were specifically targeting the CS1 era PPC machines with 630 PDS from the NuBus Architecture generation. Should be very interesting info coming up indeed.
Do you have any plans for a future passthru connector to explore expanded use of the Networking capability of the CS1 Slot?
David Cook
Well-known member
I figured I'd start with the easiest way of communicating between a microcontroller and the Mac -- using the slot's serial lines. If the card proves to be practical, then I can step up to memory transfers. That opens the door to various PDS slots and even NuBus.
That was very helpful, actually. I have a couple of Power Mac 6200s with CS1 slots that also won't show ROM address accesses. I would have spent days trying to debug that.
This brings up another concern --how will the 68040 cache affect bus snooping? In a tight loop, such as cold-boot memory tests, the bus will likely only show ram accesses. So, this whole thing is going to be a learning experience.
aperezbios
Well-known member
@David Cook, this is awesome. Have you successfully been able to transfer data serially, and if so, at what speed? I just recently made some similar PCBs, which are designed to have either an ESP8266, Raspberry Pi Pico, or generic "blue pill" board (choose one), which then attaches to the serial port. It's notched such that it can be used in either a CommSlot 1 or CommSlot 2-enabled Mac.
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David Cook
Well-known member
My board communicates at 57600 baud, no hardware handshaking. I have the pins for handshaking brought out to pad in case I want to experiment with them.
The TX pin on the slot is the Mac transmitting out. So, that should be wired to your microcontroller's RX pin.
And it follows that RX on the slot is the Mac receiving in. So, that should be wired to your microcontroller's TX pin.
By the way, there is a definite limit to the amount of power you can draw from 5V trickle. 5 ma I think. If you exceed that too much, the Mac shuts down almost immediately at power up.
The TX pin on the slot is the Mac transmitting out. So, that should be wired to your microcontroller's RX pin.
And it follows that RX on the slot is the Mac receiving in. So, that should be wired to your microcontroller's TX pin.
By the way, there is a definite limit to the amount of power you can draw from 5V trickle. 5 ma I think. If you exceed that too much, the Mac shuts down almost immediately at power up.
rabbitholecomputing
Vendor The First
Good to know, thanks, @David Cook . Can you share any information on voltage levels/logic types for the serial pins? TTL? CMOS?
David Cook
Well-known member
It is non-inverted logic level serial (0 to 5 volts). I plugged it straight into an Atmel ATMega1284 microcontroller without any additional circuitry.
That is, it is definitely not -5/+5 or -12/+12 RS232/RS422 like at the mini-din modem port at the back of the computer.
rabbitholecomputing
Vendor The First
Thanks, that's the assumption I was operating under, but it's nice to have it confirmed.
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