Hi, all - hope everyone is having a good summer (in the Northern Hemisphere). Here is a question for the experts:

if one wants to interface a 65c02 to the PSP of a PIC microcontroller, must he use a VIA or PIA (or the like) between the PIC and the 65c02's bus?

Breaking out /RWB into separate /read and /write seems simple enough, or does the connection require more? The PIC does provide a latch for the data. Finally, does anyone know of any code repositories out there for this purpose (addressing the PIC via the PSP)? I'm hardwiring all this to veroboard, so I need to get all the hardware right.

Thanks!

Jon

Nobody knows the answer, here?

I don't have knowledge of this, but... the PSP appears to be a bidirectional 8 bit port, with internal latches, and inputs for read, write and chip select. In other words, it allows the PIC to be addressed as a single location I/O device. As such, yes, it should be possible to connect directly to the 6502 bus, provided you have a bit of glue logic.

Ed, thanks! This is my first time experimenting with PIC microcontrollers. -Jon

Do let us know how you get on!

Indeed, will do!

PS I do have newer, "better" chips (e.g., the PIC18F45K40, etc.) - I just wish I knew how to create a PSP (effectively) on those. I also have a few 18F46Q84s around. I just wish I had a better handle on using them.

-Jon

Pages 8 and on of this PDF might be indicative of some possible tactics
https://owd.tcnj.edu/~hernande/ELC343/Chapter_07.pdf

Ed, this is great information - thank you!!! -Jon

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

You are 100% right, Garth - precisely why I'm using the 18F-K... speed. And, of course, the more robust feature set. However, for the purposes of testing everything, I'm just going to see if I can't get an I2C 16x2 LCD up and running via the MPU. Just for testing, though. If I can get that up and running (and I haven't figured out how to do it yet), then I should pretty much be able to interface with the more useful features.

Jon

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Garth,

Question - when you put the PIC directly on the 'c02 data bus, do you need to connect the PIC to PHI2, or do you just keep using the internal oscillator in the MCU?

-Jon

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

I too haven't used the PSP in a way more years than I'd like to remember.

I do wonder about connecting the PIC's clock input to the Phi2 clock of the 6502/65C02.

The PIC is naturally a 4 clock cycle machine. Running Phi2 into the clock input of the PIC is going to effectively force the PIC to operate at 1/4 the clock frequency of the 6502/65C02.

My initial recommendation would be to run the PIC with a dedicated clock, at or above, its maximum operating frequency, which is somewhere in the vicinity of 20 MHz. I expect that the PSP is designed to provide an interface to an external host that is operating asynchronously to the PIC. Because of this, the circuitry of the PIC's PSP should be capable of receiving data from a processor like the 6502/65C02 which is operating at a frequency that is not an integer multiple of the PIC's clock frequency.

As previously stated, there's a lot of work that the PIC's SW has to perform to make the PSP sing. Thus, my first thought is toward making the interface as efficient and fast as possible would be to run the PIC as fast as your selected component allows.

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Michael A.