ZX Spectrum 16K/48K edge connector
Notes on Connections
The !CK signal, sometimes referred to as PHICPU is available on Lower Pin 8. This clock signal is generated by the ULA and is interrupted during contended memory access. This clock signal is inverted by a transistor switch to provide a clean clock edge for the Z80.
The key slot ensures correct alignment of peripherals with the edge connector. The slot occupies the pin 5 positions
- Lower Pin 4 is connected to the +9 volt (nominal) DC supply from the ZX Spectrum PSU.
- Lower Pin 3 is connected to the smoothed +5 volt DC output of the internal 7805 regulator.
- Upper Pin 20 is connected to the -5 volt DC output of the internal power supply circuitry.
- Upper Pin 22 is connected to the +12 volt DC output of the internal power supply circuitry.
- Upper Pin 23 is connected to the oscillating voltage within the internal power supply circuitry. This is nominally 12 volts AC.
- Lower Pins 6, 7, and 14 are connected to the 0 volt rail.
Pin 15 on the lower side of the edge connector provides the same composite video signal that is fed into the UHF modulator. Lower pin 16 on the carries an inverted luminosity signal to use with the 'U' and 'V' colour difference signals provided on lower pins 18 and 17 respectively