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TESLA keyboard encoders

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Overview

TESLA are known to have produced two models of single-chip keyboard encoders for contactless keyboards. Model MH103 provides binary sequential output for use in conjunction with a separate look-up table ROM. MH113 is the “programmable” counterpart with the key definitions held internally. Both ICs are 40-pin plastic DIP packages. Both models use two-of-N encoding. A simpler MH1KK1 DIP-24chip provides 16-to-4–line binary encoding and can be used in pairs for full-size keyboards.

Models

Few details are known about these encoders. MH113 was discussed in the mailing list topic KL pro MH113 in February 2010. MH103 and MH113 are also mentioned on page 8 of the forum topic Počítač Consul 2715 about the Consul 2715 computer. The MH103 and MH113 descriptions given below are from the TESLA “blue catalogue”, and are shown in an attachment in the MH113 mailing list topic. These are the only written details known thus far for those two models; it appears that TESLA may not have published further specifications. The original Czech text has been machine translated into English and then, where possible, rewritten into a more natural translation. Some of the original machine translation remains where the meaning of the text cannot be understood in itself. Only a Czech speaker with an understanding of Soviet-era computers will be able to translate the text in detail.

Note that TESLA were not consistent about whether the model numbers contained a space; e.g. both MH 1KK1 and MH1KK1 were used. Here the spaces are omitted, to match what is seen on the ICs themselves.

Model Keys Modes Bits/key Rollover Output Data Notes
MH1KK1 16 1 Binary encoder 4-bit representation of input
MH103 120 8 Binary sequential Details on these models are unclear
MH113 120 8 Encoded output

MH1KK1

This is 16-to-4–line binary encoder. The 1983 catalogue entry for MH1KK1 describes the chip as follows:

Kodér pro bezkontaktní klávesnice v přístrojích pro přenos a zpracování dat. Úkolem obvodu je po stisknutí příslušného tlačítka klávesnice přiřadit každému hexadecimálnímu symbolu čtyřbitové binární slovo podle funkční tabulky.

This text translates to:

Encoder for contactless keyboards in data transmission and processing devices. The task of the circuit is to assign a four-bit binary word to each hexadecimal symbol after pressing the appropriate keyboard key according to the function table.

MH1KK1 is a 24-pin DIP, with the following connections: VCC, GND, 16 input lines (datové vstupy, D1–D16), 4 output lines (datové výstupy, Q1–Q4) and a pair of “selective outputs” (výběrové výstupy) W1 and W2. Each data line represents a value one less than its position number: D1 outputs 0, and D16 outputs 15. W1 and W2 are both active when any key is being pressed (including when D1 is active and thus Q1–Q4 are all zero), and are both inactive when no key is pressed. There is no indication of how clash detection is to be performed, i.e. if two or more inputs are active at once. Q1–Q4 appear to be undefined when there is no key pressed.

A pair of MK1KK1 chips can be seen in the Zbrojovka Brno Consul 259.13 keyboard.

MH103

MH103 is a binary sequential encoder, used with an external look-up table ROM. The official TESLA description is as follows:

MH 103 – kontroler klávesnice

Obvod je určený pro elektronické bezkontaktní klávesnice, kde nahrazuje stávající elektroniku (cca 20 IO složitosti SSI a MSI) s výjimkou výstupních kódovacích pamětí ROM. MH 103 zajišťuje zpracování (překódování, zapamatování, potvrzení) platných dat ze 120 vstupních míst (tlačítek). Dále zajišťuje sekvenční činnosti klávesnice, elektrickou aretaci 1 tlačítka, výkonové výstupy 50 mA, automatické opakování zvolených nebo všech tlačítek. Obsahuje 1370 hradel, napájecí proud 150 mA, výkonová ztráta 220 mW, pouzdro plastové 40 vývodů.

This text translates to:

MH 103 – keyboard controller

The circuit is designed for electronic contactless keyboards, where it replaces the existing electronics (approximately 20 SSI and MSI ICs) with the exception of the output coding ROM. MH 103 provides processing (recoding, memorization, confirmation) of valid data from up to 120 keys. It also provides sequential keyboard operations, electrical interlocking (N-key lockout), power output of 50 mA, automatic repetition of selected or all keys. It contains 1370 gates and takes a supply current of 150 mA. Power consumption is 220 mW. It uses a 40-pin plastic DIP package.

Schematics for the Zbrojovka Brno Consul 262.3 keyboard show both MH 103 and MH 113 to be two-of-N type; unlike Micro Switch schematics, the complete encoding pattern is depicted. It appears that the same PCB accepts both MH103 and MH113; the former in this instance utilises a pair of DIP-16 ROMs, listed as MH74S571 bipolar PROMs (TESLA’s version of 74S571). The sensors in this keyboard are MH3SS2, dual-output source level.

MH113

MH113 is the same encoder circuit as MH103, but the key definitions are held internally in what is likely to be mask-programmed ROM. The official TESLA description is as follows:

MH 113 – programovatelný kontroler klávesnice

Tento IO je řešen v návaznosti na MH 103. Vykonává všechny funkce jako MH 103, navíc zajišťuje kódování 120 tlačítek v 8 registrech a má volitelný interface (IRPR, standartní). Obvody MH 103 a MH 113 jsou určené pro styk obsluhy se zařízeními výpočetní techniky JSEP a SMEP a všech dalších oblastí činnosti, kde je využíváno předáváni informací. Obvod dosahuje 2140 hradel, napájení 200 mA, pouzdro plastové 40 vývodů.

This text translates to:

MH 113 – programmable keyboard controller

This IC performs all the same functions as MH 103. Additionally it provides a look-up table in ROM for 8-bit coding of up to 120 keys, and has an optional interface (IRPR, standard). The MH 103 and MH 113 circuits are intended for the operator's contact with JSEP and SMEP computer equipment and all other areas of activity where the transmission of information is used. The circuit has 2140 gates and takes a supply current of 200 mA. It uses a 40-pin plastic DIP package.