|Re: 8051 as HP-41 module? a note or two about 8051s|
Message #10 Posted by Diego Diaz on 15 Aug 2003, 3:18 p.m.,
in response to message #9 by Bill Wiese
Well Luiz, you can of course contact me for whatever I can be of any help, so can the rest of you.
First a pair of mods to my previous posts:
a) The Xtal must be slower than 26 ~ 24 Mhz, wich is the max. speed a PIC18F252 can run at from its internal resonant circuitry, and there is no space inside a module enclosure to fit an external oscilator. (Pls correct me if I'm wrong about that.)
b) You can pull the V+ line down to 3.5v with a series zener diode, this is enough for the 41 to handle the ISA line, while the 18LF252 is able to keep the 24Mhz Xtal running when powered at 3.5v thus lowering the Idd to a typical 5.5mA, 6.5mA max. wich seems quite reasonable, as the original MLDL design drawn about 12 ~ 14 mA. (not counting the EPROMS!!, they were only powered during ONE single cycle for -obvious- reading purposes.)
Now some facts:
It's about 2.77µS between clock pulses in a standard 41 (not 2x clocked) at 360kHz. The PIC needs four clock cicles per instruction so it gives us 6MIPS at 24MHz so we can process 16 instructions to handle the corresponding I/O line... It's not too much but I think it's worth trying.
Regarding the program Vassilis, I'll contact I.J. and will ask him about. I asked you because I didn't know if you were the one that developed the code, and there is no downloadable file in your page nor Mr. Ioannidis'. Is this code copyrighted? or is it only a "Coca-Cola formulae alike" well keep secret...? :-)
I'm starting the PIC18F252's thick PDF Data Sheet reading, I've also already done the flowcharts for the corresponding port B interrupt handling, and hope to begin testing (and a huge amount of debugging) as soon as my PIC programmer is ready.
Trying to keep 41's alive.