User Port

One of the most commonly used ports at all. Many extensions like parallel floppy speeders, eprommers, relay cards, etc. connect to the user port. Please note that the SX-64's user port seems to be slightly INCOMPATIBLE which means that certain user port devices can cause DAMAGE! See description of pin 10-11.

Connection scheme

ASCII version:

      1   2   3   4   5   6   7   8   9   10  11  12
  +--===+===-===-===-===-===-===-===-===-===+===-===--+
  |     |                                   |         |
  +--===+===-===-===-===-===-===-===-===-===+===-===--+
      A   B   C   D   E   F   H   J   K   L   M   N

Signal Description

Pin(s)	Signal	Dir	Description
1	GND	-	Ground (0V).
2	+5V DC	-	Supply voltage. Max. 100mA.
3	/RESET	in/out	RESET. When pulling this line to LOW, the CPU resets and waits for a LOW-HIGH transistion to load the PC with the value stored in $fffc/$fffd. After power-up, timer A in the NE556 pulls this line to LOW for a short time and half a second later back to HIGH.
4	CNT1	progr.	Count1. Connected to CNT of CIA #1.
5	SP1	progr.	Serial port 1. Serial I/O of shift register (SP) of CIA #1.
6	CNT2	progr.	Count2. Connected to CNT of CIA #2.
7	SP2	progr.	Serial port 2. Serial I/O of shift register (SP) of CIA #2.
8	/PC2	out	Port control 2. Connected to /PC of CIA #2. Becomes LOW for one cycle after read or write access of port register B. Open collector output, therefore needs pull-up resistor.
9	SER ATN	out	Serial attention. Attention line of serial bus. Can be used as output (inverted PA3 of CIA #2) and via open-collector ouput as input, too (have to verify that).
10-11	9 VAC	-	Supply voltage. Max. 100mA. WARNING! It is said that one of the pins is GROUNDED in the SX-64! This means for example that you cannot use your Commodore Vicmodem, because it will damage your SX-64! [2]
12	GND	-	Ground (0V).
A	GND	-	Ground (0V).
B	/FLAG2	in	A negative edge at this pin sets the FLAG bit in the interrupt control register of CIA #2.
C-L	PB0-PB7	progr.	Port register B of CIA #2. Each line is individually programmable as in- or output.
M	PA2	progr.	Port register A, bit 2 of CIA #2.
N	GND	-	Ground (0V).

^* The 'ø' is used as Greek 'phi' here.
progr. = programmable

Note: All pictures show the plug side.

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