COMPUTE II ISSUE 3 / AUGUST/SEPTEMBER 1980 / PAGE 12

The FIRST MATE/SECOND MATE By Micromate

An Evaluation: Marvin L. De Jong

Ever since I began doing experimental work with 6502 single-board microcomputers, such as the KIM-1, SYM-1, and the AIM 65, I have looked for a neat and convenient way for my students and me to breadboard circuits to be interfaced to the microcomputer. The FIRST MATE/SECOND MATE combination by MicroMate, P.O. Box 50111, Indianapolis, IN 46256 will probably end my search. In my opinion, this system is an excellent way to prototype and interface circuits to the microcomputer. It will be of great interest to engineers, technicians and experimenters as well as to those of us involved in technical education.

The SECOND MATE is simply a 2½" by 3½" printed circuit board with a 22/44 pin edge connector on one side, and a set of 44 printed circuit pads that duplicate the application and expansion edges on the KIM-1, SYM-1 or AIM 65. Thus, the SECOND MATE is transparent to any other devices you may want to connect to your microcomputer. Finally, the SECOND MATE has a 40 pin connector that connects to a 40 pin DIP jumper that connects the SECOND MATE to the FIRST MATE by a 40-strand ribbon cable. The DIP jumper is about 6" long. Thus, the SECOND MATE is connected to the microcomputer with the usual 22/44 pin edge connector, and the FIRST MATE connects to 40 of the 44 lines that are available at these connectors.

The FIRST MATE is a 7½" square printed circuit board upon which is mounted an SK-10 breadboard, three 40-pin connectors, a position for a second SK-10 or another protoboard, four “universal” connectors for GND, + 5V, + V and a –V supply. An LED indicates when power is applied, and several filter capacitors are also provided. The three 40-pin connectors on the FIRST MATE connect to either the expansion connector, the application connector or, if you have a SYM-1, the so-called AA connector. Suppose you wish to interface a circuit to the expansion connector on your microcomputer. The 40-pin DIP jumper is then connected to the 40-pin expansion connector on the FIRST MATE, while the SECOND MATE is plugged into the expansion port on the microcomputer.

The eight data lines, the sixteen address lines, and eight control lines are then connected to labelled locations on the SK-10. Each labelled location allows up to five wires to be connected. The control lines are the usual ones, R/W, 0₂, RES, NMI, IRQ, RDY, SYNC, and one device select line. (For the SYM-1, the device select is the 18 line. Some minor trace cutting and jumpering gives the CS8 line or another device select for the AIM 65.)

If the FIRST MATE/SECOND MATE are connected to the application port, then the eight pins of Port A and the seven pins of Port B may be accessed on the SK-10 at labelled positions. Note that both the SYM-1 and the KIM-1 do not allow a connection to PB6 at the applications port. If you want to use the FIRST MATE with an AIM 65 you will probably want to jumper PB6 to the SK-10 as well as the control lines CA1, CA2, CB1, and CB2 from the VIA. This would be quite simple, but it would eliminate (or duplicate) same pin functions for the AA connector on the SYM-1. Connections can also be made to the expansion port and the applications port simultaneously if two SECOND MATES and two ribbon cables are purchased.

The geometry of the First MATE was designed to mount on a SYM-1 with nylon spacers and screws. The FIRST MATE can probably be placed on a KIM-1 with no problems. For my AIM 65 I chose to build a little table consisting of two 4" × 8" pine legs and a 14" × 8" masonite perforated board for a top. This not only makes a dust cover for the AIM 65, but it also keeps me from yelling at the cat when he decides to sleep on my microcomputer. If the little table is made about 8" deep then the printer paper can be easily seen, The FIRST MATE can be bolted to the perf-board top. I think it made a neat system, allowing me to work directly over the microcomputer when I was breadboarding a circuit.

Clearly the FIRST MATE was designed for the SYM-1, but with a few simple modifications, some of which are suggested in the literature supplied with the FIRST MATE, it can be used with the AIM 65. No modifications are necessary for operation with the KIM-1. To put the FIRST MATE to the test, I breadboarded the simple stepper motor interface described in this issue. No modifications to the FIRST MATE were required for this circuit.

Although there are other breadboarding schemes available (see TERC, 575 Technology Sq., Cambridge, MA 02139 for other possibilities) that are not being evaluated here because I have little or no experience with them, I can wholeheartedly recommend that you examine the MicroMate system for $87.50. I think it is an excellent approach to circuit development. I would like to see an AIM 65 version of the system for sale, but the modifications are quite simple.