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24 pin DZM 12 DREH connector layout
24 pin DZM 12 DREH connector

Top side

2+5VDC(100 mA max)
3/RESETReset, will force a Cold Start. Also a reset output for devices.
4CNT1Serial port counter from CIA #1
5SP1Serial port from CIA #1
6CNT2Serial port counter from CIA #2
7SP2Serial port from CIA #2
8/PC2Handshaking line from CIA #2
9ATNThis pin is connected to the ATN line of the serial bus
10+9VAC(+ phase) Connected directly to the Commodore 64 transformer (100 mA max)
11+9VAC(- phase) Connected directly to the Commodore 64 transformer (100 mA max)

Bottom side

B/FLAG2The Commodore 64 gives you complete control over Port B on VIA chip #1. Eight lines for input or output are available, as well as 2 lines for handshaking with an outside device. The I/O lines for Port B are controlled by two locations. One is the port itself, and is located at 56577 ($DD01 hex). Naturally you PEEK it to read an input, or POKE it to set an output. Each of the eight I/O lines can be set up as either an input or an output by setting the data direction register properly. It is located at 56579 ($DD03 hex).
According to 2 reports in our database (2 positive and 0 negative) the Commodore 64 / 128 User I/O pinout should be correct.

Is this pinout
Source(s) of this and additional information: Commodore 64 User Manual, Commodore 64 Programmer"s Reference Guide
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