The module has the following features:

• Two servo control signal generators
• Single OUT instruction to set each servo position
• Easily set from BASIC or other environment
• Tight address decoding
• Compatible with the RCBus
• Compatible with RC2014 systems

SC609 is a two channel servo controller. It has tight address decoding and easy access with a single OUT instruction to set each servo position.

The address decoding is such that one module takes only two I/O addresses (one for each servo channel). Only writes to those addresses are decoded, so those addresses could be allocated to another device that only has a read function. Many of these modules can be installed in a single system as long as there are no address conflicts.

The output of each channel is set by writing a value from 0 to 255 decimal to the port address of the servo channel. A value of zero turns the pulses off, leaving the output signal at a steady low level. A value of 1 produces the most narrow pulse and 255 the most wide pulse.

Typically, a servo requires a pulse between 1 ms and 2ms. The pulse needs to be repeated about 50 times a second. If no pulse is detected the servo will not move. With a 1.8432 MHz oscillator fitted, a 1 ms pulse is produced when a value of 115 is written to the servo port and a 2 ms pulse is produced by the value 230. The pulses are repeated every 17.8 ms (56.25 Hz).

If the base I/O address is set to 6, then to set the value of the servo pulse width you need to write the value to I/O address 6. Servo #2 width is set at I/O address 7.

To set the width of servo #1 channel to 200 (decimal) in BASIC:

• OUT 6, 200

To set the width of servo #1 channel to 200 (decimal) in assembler:

• LD A, $C8
• OUT (6), A

Documentation

The documentation can be found at www.smallcomputercentral.com

Compatibility

This module conforms to the RCBus specification v1.0 for 40-pin systems.

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.

Complete Systems

If you are looking for a complete system the following products might be appropriate.

• SC126 RCBus-80pin Z180 RomWBW CP/M Motherboard
• SC720 RCBus-80pin Z80 RomWBW CP/M Motherboard
• SC791 RCBus-80pin Z80 RomWBW CP/M Computer
• SC792 RCBus-80pin Z180 RomWBW CP/M Computer
• SC114 RCBus-40pin Z80 SCM & BASIC Motherboard
• SC131 Pocket-sized Z180 RomWBW CP/M computer

Notes

• This product is supplied as a kit of parts that require assembly.
• It is your responsibility to pay any import duty or taxes charged by your home country.
• This product is designed for hobby use and is not suitable for industrial, commercial or safety-critical applications.