RPN-65 Question.

[teenix]

From the emulator, RAM [20] and [21] are used for trig calculations and RAM[22] doesn't appear to be used for anything. This is strange as I thought with the cost of chips in those days, it would have some use.

RAM[20] stores the Last X value too, so if you do a trig function, the Last X is lost. I wonder why RAM[22] wasn't used for Last X then.

I suspect there just wasn't enough ROM to code in a different address for Last X using RAM[22], as the Microcode that sets up the address for RAM[20] is a common routine between trig functions and Last X.

cheers

Tony