Articles tagged “PG12864LRS”
2MHz should be enough for anyone
LCD Timing
Last time I discussed the hardware I mentioned I had LCD timing issues. I have finally resolved them, but this has been the most time consuming part of the project so far. The first thing to sort out was the LCD's E pin. Once you have set up the LCD's input pins to a state where they're ready to read or write data, you need to drive this pin high. I had had some success by holding it high permanently and relying on the Z80 to set all the other to the right state at roughly the same moment, but this was inaccurate and resulted in occasional display glitching.
Comments Electronics Emerson LCD PG12864LRS Z80 Z80 computer
Z80 computer with a primitive I/O board
A computer needs some way of interacting with the outside world via input and output devices. It's about time, then, that the Z80 computer project acquires a section dedicated to I/O. The Z80 differentiates between memory and I/O devices, though both share the data bus and the address bus. You can control I/O devices using the in (input) and out (output) instructions. When you input or output you must specify a device address and a value or target register. For example,
in a,($20) ; Read a value from device $20 and store it in A.
Back to Hardware
I enjoy dabbling with low-level programming, but have never actually built a computer to run these programs. I think it's time to correct that, and as the BBC BASIC project has required me to develop an almost complete Z80 OS (the only thing that's left for the TI-OS to do is manage files) I thought a Z80 computer would be a good start. The planned specs are (as a starting point):
10 MHz Z80180 CPU;64KB RAM (2 32K×8 SRAM chips);128KB Flash ROM;Graphical LCD;Simple joypad input;Keyboard input (AT using either software AT routines or dedicated microcontroller).
Comments Electronics LCD PG12864LRS PICAXE PICAXE-28X1 Z80 computer