COSMAC forces
The article by David Bolton on Easy 6502 in the LXF312 issue caught my attention. Back in the late 1970s, I was tasked with both learning assembler and writing a data acquisition program for our newly developed eddy correlation environmental flux machine called the Hydra. I had only programmed Fortran up to that point.
I was provided with an RCA COSMAC Microboard Computer with 8-inch floppy disks using the new RCA 1802 CMOS microprocessor and told I had not much more than six months to do it. Assembler programming teaches you not to be sloppy in your programming. The whole program took up 16 fan-folded pages. I even invented a magnetic tab A4-sized tablet that allowed me to stack what was being loaded-unloaded into/from the various data and program registers.
The system took sensor readings at 10Hz – we wanted to do it at 20Hz, but the speed of the processor and what it was being asked to do meant that even at 10Hz, getting all the data in and processing it took up 95ms of each 100ms cycle. Because of that I had to reserve a 100ms cycle at the end of each hourly data collection and processing period to work out all the various sums, means and variances. This was also our first experience with solidstate memory packs – a 16Kbyte CMOS paperback-sized module from GK Instruments, Milton Keynes.
You can find the paper here: www.sciencedirect.com/science/ article/abs/pii/0168192384900947
Colin
Neil says…
I love it when our readers let us know what they’ve been up to in the past (and present), so many thanks for taking the time to write in. David’s going to write a bit more on 6502 down the line; we’ve got a C-to-6502 assembly compiler in the works.