6581 / 8580 Signal Description ------------------------------ Pin(s) Signal Dir Description 1-2 CAP ? Capacitor #1 for the programmable filters. 1A/B 6581: 470pF, 8580: 22nF*. Note that both capacitors (see pin 3-4) should have the same value. [1] recommends 2200pF for normal operation, which was AFAIK never used in the C64. 3-4 CAP ? Capacitor #2 for the programmable filters. See 2A/B pin 1-2. 5 /RES in RESet. If this line remains LOW for at least 10 ø2 cycles, all internal registers reset to zero and the audio output is turned off. 6 ø2 in Phi2**. System clock cycle. All data bus action takes place only when ø2=1. 7 R/-W in Read/Write. 0=write access, 1=read access. 8 /CS in Chip select.0=data bus valid, 1=data bus high impedance state (tri-state). 9-13 A0-A4 in Address bits 0-4 for selecting one of the 29 registers. 14 GND - GrouND (0V). To reduce noise, this line should be connected separately to the power supply. 15-22 D0-D7 in / out Data bits 0-7. 23 POT Y in Potentiometer Y. Analog input #2 for paddles. (ADC#2) 24 POT X in Potentiometer X. Analog input #1 for paddles. (ADC#1) 25 Vcc - Supply voltage. +5V. 26 EXTERN in External Input. Max. input 0.6V. IN 27 AUDIO out Audio output of all voices. OUT 28 Vdd - Secondary voltage. +12V (6581) or +9V (8580). * You might find 330pF in some boards, too. ** The 'ø' is used as Greek 'phi' here. ------------------- [1] C64 Programmer's Reference Guide (excerpt) Author: Marc-Jano Knopp on 97/11/21 Source: http://mjk.c64.org