An STDbus version. Probably the design that was ported to STEbus.

The STEbus writes output port bytes to an edge-triggered latch, and reads input port through an 8-bit buffer.

The STEbus writes command bytes to an edge-triggered latch.

The microcontroller writes response bytes an edge-triggered latch.

The actions set flags to say a latch is full, and clear them when a latch is read.

This communication through one-byte back-to-back latches is extremely simple and can easily be used for communicating with any other slave processor. There are six in the BBC Micro's Tube interface. To keep things simple, I would look at J.G. Harston's tube-through-a-single-channel software.

SEMC

The SEMC and SEMC-10 use an intelligent LSI chip set which provides all the functions required to drive a servo motor without interaction from the host computer. It has inputs for an encoder and resolver, and produces a control voltage and pulse signals to drive a servo amplifier.

The SEMC accepts motion commands and position information over the STEbus or via an RS232 link. Commands, which may be repeating sequences, are in a simple ASCII format. The SEMC can perform a complex command sequence and interrupt the main STEbus CPU when it has finished.

There are two limit switch inputs, 8 general-purpose TTL inputs which may optionally be used as resolver inputs and 8 general-purpose TTL outputs on the 50-way connector, which conforms to the Arcom standard signal-conditioning scheme. In addition this connector also carries the control voltage out and inputs for right and left limit switches, direction and stop/start signals. The SEMC and SEMC-10 occupy 3 I/O locations on the STEbus.

SEMC-10 has all the features of the but has additional motion and position commands allowing complex profiles to be generated in systems.

Power consumption:

(from STEbus): 0.8A typical at 5V

Features:

• analogue and PWM control output
• encoder or resolver feedback options
• STEbus or RS232 communication option
• STEbus interrupts on sequence completion
• LEDs for debugging