**Note: All measurements below were using a x10 probe, but I forgot to set the scope to show that.  So rather than the 100mv/division that shows in the photos, I was actually using 1.0v/division.

IC-5 is an 8-Channel Data Selector switch that is used to read the status of various switches or buttons from the front of the rig, as well as the microphone.

The Processor (IC-1) chooses which data input line to read by setting an address on pins 11-13, and setting the Disable pin low. IC-5 then passes the state of the selected input line to the processor on pin 14.

TC4512 Pinout


IC-5 Pin 1: RXB (Receive) mode

IC-5 Pin 1: RXB(Low active)


IC-5 Pin 2: HLD (Hold Button Active Low)

IC-5 Pin 2: HLD (Not pressed)


IC-5 Pin 3: Not used

IC-5 Pin 3: Not Used


IC-5 Pin 4: AM/FM buttons (Not pressed)

IC-5 Pin 4: AM/FM

IC-5 Pin 5: LSB/USB/AM/FM Switches (Not pressed)

IC-5 Pin 5: LSB/USB/AM/FM Switches

IC-5 Pin 6: Microphone LSB/CW/AM Switches (Not pressed)

IC-5 Pin 6 LSB/CW/AM Switches

IC-5 Pin 7: Microphone UP/DWN Switches (Not Pressed)

IC-5 Pin 7: Mic UP/DWN

IC-5 Pin 8: GND

IC-5 Pin 8: Ground


IC-5 Pin 9: Normally High, but my radio has a mod that uses this line…

IC-5 Pin 9: Normally tied high, but not this radio


IC-5 Pin 10: GND

IC-5 Pin 10: Ground


IC-5 Pin 11-13: Data Select Lines A, B C

IC-5 Pin 11: Data Select A


IC-5 Pin 12: Data Select B


IC-5 Pin 13: Data Select C


IC-5 Pin 14: Data Output to processor

IC-5 Pin 14: Data Output Z


IC-5 Pin 15: Disable (Like a chip select low)

IC-5 Pin 15: Disable


IC-5 Pin 16: +5 volt source

IC-5 Pin 16: +5 volt source