26-02-2020, 11:29 AM
Hi Ernest,
Back in the 1970's and 1980's it was deemed that a parallel interface was the way to go because one effectively could transfer data quicker that a single wire serial interface such as RS232.
However sending data in parallel at higher speeds is subject to synchronisation problems and now in the 21st century where back using serial interfaces where this is not an issue.
The mouse interface consisted of an 8 bit parallel bus DAC of that era but to make the interface use less wires all the data is sent through a shift register in exactly the same way as the video shift register of the microbee. In addition there is a Chip select line and separate clock line. For the mouse we're mainly just pumping data back from the DAC but with an additional transmit shift register we can also send it data/commands. To support multiple devices an additional device select flip flop is added.
These days the design can be squashed into a single IC, but back then it consisted of 12 LSI ICs.
Someone
Back in the 1970's and 1980's it was deemed that a parallel interface was the way to go because one effectively could transfer data quicker that a single wire serial interface such as RS232.
However sending data in parallel at higher speeds is subject to synchronisation problems and now in the 21st century where back using serial interfaces where this is not an issue.
The mouse interface consisted of an 8 bit parallel bus DAC of that era but to make the interface use less wires all the data is sent through a shift register in exactly the same way as the video shift register of the microbee. In addition there is a Chip select line and separate clock line. For the mouse we're mainly just pumping data back from the DAC but with an additional transmit shift register we can also send it data/commands. To support multiple devices an additional device select flip flop is added.
These days the design can be squashed into a single IC, but back then it consisted of 12 LSI ICs.
Someone