This theory is backed up by comparing the oscillator and initialisation circuitry around the processor with datasheets for other ‘pre‐programmed’ TMS1000 variants. Since processor development, coding and the tools required for coding were very expensive and time consuming to make in 1977‐78 it is safe to assume that the MB4850 is a variant of the TMS1100 which was packaged and programmed specifically for the Simon game (TMS1100 were not programmable by the customer, the customer had to specify the required ROM image (software) and then the chips would be manufactured with the ROM image included). Pocket Simon mock‐up on a breadboard MB4850 MicroprocessorĪccording to sources on the web the original design for the Simon game was performed on a Texas Instruments TMS1100 microprocessor which was a popular embedded processor at the time. There are also 3 wire‐links, 4 bulbs (2.5‐3V) and a piezo buzzer included. U2 – SN75494N Hex Digit Driver (the datasheet for this chip is available on the web as the National Semiconductor DS75494 Hex Digit Driver datasheet).C2 – 47nF capacitor (this is an old‐style capacitor with colour code yellow, violet, brown, silver, silver and can be replaced with an equivalent ceramic capacitor (usually marked ‘471’)).1uF ceramic capacitor (usually marked ‘104’) R2 – 22K resistor with 5% tolerance (colour code red, red, orange and gold).R1 – 680K resistor with 5% tolerance (colour code blue, grey, yellow and gold).The internal hardware of Pocket Simon consists of a single sided circuit board containing 4 components and 2 integrated circuits (all soldered directly to the circuit board): There are 2 sliding switches on the game (on the full‐sized game there is an additional on‐off switch which in the pocket version is replaced by a two‐pole game switch):
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