A later design is now available: SC718

This module houses a Z80 counter/timer (CTC) device (Z84C30xxPEG) and is designed for use with RCBus retro computers.

The Z80 CTC provides four counter/timer channels and this board provides a range of input and output options for each channel.

Each channel has the following input options:

• Bus clock CLK
• Bus clock CLK2
• On-board oscillator
• Bus user pin

The bus CLK2 signal can be optionally linked to:

• CTC channel 0 output
• CTC channel 1 output
• CTC channel 2 output
• On-board oscillator

By connecting CLK2 to a CTC output it is possible to set the baud rate of a Z80 SIO/2 module by writing a suitable value to the CTC.

Each input and output is available on a pin header mounted on the back edge of the board. This header is well suited to linking to prototypes with Dupont cables.

The module provides support for Z80 mode 2 interrupts, with the IEI and IEO signals available on a two pin header for linking with flying cables. These signals can also be optionally connected to the RCBus with jumpers.

Address selection is by DIP switch, allowing the module to be located on any 4-byte I/O address boundary. The tight and flexible address decoding means many of these modules can be fitted to a single RCBus computer.

Features

• Tight address decoding
• Address selection via DIP switch
• Flexible input signal selection with jumpers
• Easy access to input and output signals on header pins
• Optional output to RCBus bus CLK2 signal
• Interrupt daisy chain signals can be jumpered to bus or use flying leads
• On-board clock source which can also be used for the main bus clock
• Works with 40-pin, 60-pin and 80-pin backplanes
• Extra options when used with enhanced backplanes

Documentation

This product has a user guide and an assembly guide. These documents can be found by following the documentation link below.

Compatibility

This module conforms to the RCBus specification v1.0 for RCBus-2014 enhanced 39-pin long modules.

The printed circuit board outline conforms to the RC2014 standard for full height modules.

The module is compatible with all RC2014 backplanes, all RCBus-2014 backplanes (RC2014 compatible including SC100 series) and all full RCBus 80-pin backplanes (including SC700 series). When used with 40-pin backplanes some of the features of this module are not available. The interrupt daisy chain can be implemented with Dupont cables if not supported by the backplane.

When used with a 40-pin backplane the pins in the second row are not connected. As a result the enhanced bus CLK2 signal is not available as an input or output for the CTC. The clock sources are then restricted to the main bus clock (CLK) and the onboard oscillator. Either of these sources can be used to generating periodic interrupts.

When used with a 60-pin backplane the CLK2 signal is available but the optional inputs to channels 0, 1 and 2 are still not available. The CLK2 signal is often used as a baud rate source for the second serial port in the system.

A similar design SC718 is also available. It is compatible with the RCBus, including the RC2014 standard 40-pin bus, the RC2014 enhanced 60-pin bus and the extended 80-pin RCBus.

The RCBus specification includes RCBus-2014 (both RC2014 standard 40-pin bus and RC2014 enhanced 60-pin bus) and also the full 80-pin RCBus. The 80-pin RCBus provides support for advanced Z80 features, such as the interrupt daisy-chain, as well as support for other processor families.

The kit

This kit includes all the components needed to make the module, as shown in the first picture. Other modules and backplanes shown in the pictures are not included. You will require tools, solder, and cleaning materials to assemble this kit.

Printed Circuit Board

The printed circuit board is available on its own here.

Notes

• This product is supplied as a kit of parts which require assembly.
• It is your responsibility to pay any import duty or taxes charged by your home country.
• My products are made in accordance with the "designed for RC2014" labelling scheme.
• RC2014 is a trademark of RFC2795 Ltd.
• This product is designed for hobby use and is not suitable for industrial, commercial or safety-critical applications.