Sunday, 22 October 2017

Commodore 64 C Internal SD2IEC

The standard SD2IEC connected to the IEC port on a range of Commodore computers and replaces a traditional IEC disk drive such as a 1541. Sometimes it can be more convenient to have this integrated into the computer.
This is an SD2IEC Classic from The Future Was 8 Bit, which is all the functionality on a single PCB. I have previous described fitting one inside a Commodore VIC20 - VIC20 Internal SD2IEC.
This time, I am going to fit one inside a Commodore 64C. The procedure is much the same. Full pinout can be found on the TFW8B website. The are pins for power and data, and connecting buttons and LEDs etc.. For most applications, if you're not disk swapping, you can get away without the buttons, so we only need the 5 wires indicated below.
Three on the top, and two on the bottom (the 'Reserved' pin is not used, so can be ignored).
You can solder direct to these pads, but I prefer to fit a connector, here I used a 2x3 0.1" header.
There are various points you can connect this to on the C64 board, directly to the pins on the 6 pin DIN socket is the usual way, but I prefer to find somewhere I can connect on the top of the board. Tracking the pins back to a set of diodes, the three data lines can be located, Data on the junction of CR11 and CR15, Clock on CR12/CR16 and Attn on CR13/CR17.
Here I desoldered the diode leg at the appropriate point, inserted the wire and then soldered both in place. The power connections I took from capacitor C1 near the datasette port. You can do the same thing with the capacitor legs, but here I moved it to two via holes nearby.
Those wires are connected to a 6 pin connector and attached to the SD2IEC classic, which is fitted on top of the modulator box using foam pads.
The spacing works out nicely as the card sticks out over the cartridge port, but you can see from the side view there are no clearance issues.
The connector is clear of the other side of the modulator, so no issues with shorting out on it's case.
You might have spotted the case in some of these photos is actually a breadbin C64 case, not a standard C64C one. This is because I am currently doing some development work on a C64 cartridge, and the C64C has a bar over the cartridge port which blocks access to the ROM chip.
I have moved to the C64 case which doesn't have that bar, so I can continue development work with full access (I have also removed the cartridge shield, but you don't need to do that to fit the SD2IEC).
You can still use the original IEC port to attach other SD2IEC devices or real disk drives. The same rules apply as normal, make sure the device ID's don't clash. Most default to ID8, and most can be changed on the fly to one of the other addresses.
I have fitted these before in various C64C cases. The positioning of the board means the LEDs shine upwards. The C64C has thin plastic grills in that section of case. This means when accessing the disk, you get clear disk activity lights shining through the case.
You can take that further and use a clear C64 case, if you're into that sort of thing.

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