Cytron Technical Forum

Project Name: An Experimentation on SRAM chips, using PMP and SRAM.

Author/Designer: YH

Project Description:From this experimentation using SRAM, the only other thing which has a lot of pins is the SKPIC32. So, we will use the SKPIC32 and make use of the Parallel Master Port (PMP) to interface with the parallel SRAM without much hassles.

PMP is run in 8-bit data mode, and using seperate address and data lines.

Hardware: 62256 SRAM or bigger (Alliance's AS6C4008 and others), SKPIC32, a lot of jumper wires (27 and above), 16x2 44780 LCD, breadboard.

Schematics:

Wire up the SKPIC32 according to the memory addresses and data lines in brackets.

SRAM using Alliance AS6C4008. First 64k addressable in this example.

Address:
PMA0 (A0) -> RB15
PMA1 (A1) -> RB14
PMA2 (A2) -> RG9
PMA3 (A3) -> RG8
PMA4 (A4) -> RG7
PMA5 (A5) -> RG6
PMA6 (A6) -> RA10
PMA7 (A7) -> RA9
PMA8 (A8) -> RF5
PMA9 (A9) -> RF4
PMA10 (A10) -> RB13
PMA11 (A11) -> RB12
PMA12 (A12) -> RB11
PMA13 (A13) -> RB10
PMA14 (A14) -> RD11
PMA15 (A15) -> RD10

Other unused memory address lines are tied to ground!

Data:
PMD0~7 (D0~7) -> RE0~7

Control lines:
(/CE) -> RF0
PMWR (/WE) -> RD4
PMRD (/OE) -> RD5

LCD Port:
DB4~7 -> RA0~3
RS -> RA4
EN -> RA5

Source Code: Attached.

Photo:





Compiler: MPLAB X IDE 1.10, XC32 v1.00

References: PMP Reference - http://ww1.microchip.com/downloads/en/DeviceDoc/61128D.pdf

I have interfaced 128K static RAM with PIC 16f884. Some time ago.
I even made LED panels for address/data bus.

One 16bit bus is used for data, and that is also latched for the address.

The control program (in assembler) just to write a pattern into the RAM, and read it back is actually complicated, and stretching over pages. It works, however.

The wires used are a big mess, all soldered...

I won't use this further, in favour of the PCI PCBs that I bought recently.

But I think it's better to use a PIC which has hardware support for external RAM.

takao21203 WROTE:I have interfaced 128K static RAM with PIC 16f884. Some time ago.
I even made LED panels for address/data bus.

One 16bit bus is used for data, and that is also latched for the address.

The control program (in assembler) just to write a pattern into the RAM, and read it back is actually complicated, and stretching over pages. It works, however.

The wires used are a big mess, all soldered...

I won't use this further, in favour of the PCI PCBs that I bought recently.

But I think it's better to use a PIC which has hardware support for external RAM.

That's pretty cool.

I agree that wiring it can be a difficult and nasty job. In fact, I have to wire all these in a weekend, actually.

Some Atmel AVRs have connections to external SRAM for expansion too, if I'm not mistaken.

The wiring for my 16f884 based 68000 bootloader is worse.
Actually it took me a long time to do it.

It works! It can write patterns to RAM, and read back, 128Kbyte X 16bit.

But it was too much effort to develope it further.
Actually rebuilding from start using the PCI backplane takes less time altogether!

There is serial LED display, and 2 LED panels for the data bus/address bus.
And the RAM chips between the two PCB. with a lot of wire that is not seen.

There is not schematic so it takes an hour or so each time I do more work on it.
PCI should be easier to maintain...

If I find so much time one day. The magnet wire was also hard to use, remove the isolation each time.