SC132, v1.0, User Guide

SC132 is a two channel asynchronous serial interface module based on a Z80 SIO/0 and designed for the RC2014 bus.

This module is software compatible with modules based on the Z80 SIO/2, such as:

It is therefore compatible with the following RC2014 firmware:

  • Small Computer Monitor
  • Official RC2014 firmware images 2, 4, 6, 88, 9
  • RomWBW with SIO support enabled

For compatibility with the official RC2014 SIO module, the address should be set to 80 (hexadecimal) and the clock source should be 7.3728 MHz.

Quick Guide to Jumpers

As a quick guide to getting started: Fit a jumper shunt in the position shown below.

JP11 sets the module’s I/O address to hexadecimal 80, which is the standard address for the primary serial module in a system.

JP5 and JP6 select the bus clock as the clock source for the Z80 SIO. Most software assumes the SIO has a 7.3728 MHz clock .

Serial Ports

The module has two asynchronous serial ports. These are 5 volt FTDI style ports.

The pin-out, below, describes signals with respect to SC132, so an output is a signal from the SC132 to a computer or terminal.

1Ground (GND)
2Request To Send (RTS) output
3Vcc (5V)
4Recieve Data (RxD) input
5Transmit Data (TxD) output
6Clear To Send (CTS) input

A typical FTDI style serial adapter is illustrated to the right.

This is fitted to the serial port by a 6-way Dupont cable.

The default serial port settings are as follows:

Baud rate115200
Data bits8
Stop bits1
Flow controlHardware (recommended)

The default serial port connection is P2, Serial Port A.


SC132 is typically connected to a computer or terminal with an FTDI style serial adapter. This adapter can, optionally, provide power for the whole retro system. Alternatively, this module can be powered from the backplane.

To enable power from serial port A (P2), fit a jumper shunt to JP3. To enable power from serial port B (P3), fit a jumper shunt to JP4.

WARNING: You should normally only connect one power source to the system at a time.

As power can flow either way, the jumpers, JP3 and JP4, also enable serial devices to be powered from this module.

Bus signal options

Jumpers JP1, JP2, JP7, JP8, JP9, and JP10 enable some signals to be optionally connected to the bus.

SignalJumperBus pin
TxAJP735 (TX)
RxAJP836 (RX)
TxBJP975 (TX2)
RxBJP1076 (RX2)

Signals IEI and IEO support a Z80 mode 2 interrupt daisy chain. Jumper shunts should only be fitted to JP1 and JP2 if you have a backplane set up to use pins 38 and 39 as an interrupt daisy chain. A daisy chain is not required unless you have suitable hardware and software to support it.

Jumper shunts can usually be fitted to JP7 to JP10 as these bus signals are specifically for the serial signals Tx and Rx. The only reason to not fit them is if you have another device on the bus that would conflict, such as a second serial module.

Clock sources

This modules allows each SIO channel to be clocked from either the main bus clock (typically 7.3728 MHz), the secondary bus clock, or the optional on-board oscillator (X1). Jumpers JP5 and JP6 provide these options.

Homebrew 8-bit retro computing