Project Description

This page has download links to sources for various pieces of software that I have worked on and customized, produced from scratch, or great packages I have built from sources.. You may find some of the bits and pieces useful. These packages are all configured for the FPGA_Z80 board running my custom FPGA image based on Grant Searles work. Download links are at the bottom of this page.

• DS1305.C - This is a bit of C code that talks to a DS1305 Real Time Clock chip. It can be run in an interactive mode which lets one explore all the functionality of the chip like reading the time, setting the time, setting alarms, reading and writing individual registers, setting CPM3 system time from the RTC, and reading and writing to the nonvolatile ram area. It can also be called from the startup file PROFILE.SUB to set the CPM3 clock from the RTC chip (Use "ds1305 S" as the command line). The code directly interfaces to 3 output bits and 3 input bits of a port to implement a bit banged SPI protocol to talk with the chip. I use this code with my FPGA_Z80 board. This code is written to be compiled by BDS C version 1.6.


The above image shows the logic analyzer results when bit banging a byte write command to location 37 (25H) with a data word of 15 (0FH). Note the 16 bit command/data on the SDI line being clocked by the falling edge of the SCLK line. The first bit is a one, indicating a write command, the next 7 bits are the address of 25H. The following 8 bits are 0FH. The whole command takes about 2.1ms to send to the RTC.

The above image shows bit banging a read command of address 25H. The first 8 bits on the SDI line is the read command and address. The next 8 bits on the SDO line (0FH) is the data being sent back from the RTC chip. Again, the sequence takes right around 2ms to complete. The SCLK signal is a little different shape between the write and read portions of the cycle due to an extra instruction in the write loop. This is insignificant as the SPI data all depends on the falling edge of the SCLK.


• CWTUTOR2.ASM - This 8080 assembler code uses the buzzer output on the FPGA_Z80 board to send code practice in various forms at 25WPM. It can run character by character practice, random 5 letter groups in 2 formats, 500 common english words, or continuous "PARIS " strings to calibrate the WPM speed.



• SCBTIME.ASM - This assembly language program displays the raw time variables used internally by CPM3. It was very helpful in debugging various CPM time related routines. The CPM command "DATE" can be used to set the SCB variables to various dates and these can then be dumped using this utility and compared with data generated by user programs that manipulate the system time. The big challenge in setting the CPM time from a real time clock chip is that the clock chips use a variety of representations for the time in their internal registers. This RTC internal format must be converted to the 5 byte long CPM3 time structure format. You can look at the source for the DS1305 project above to see how this can be accomplished.



• FIND.ASM - This assembly language program searches a range of files for a specified character string. It is like a simple version of the unix grep utility. The specified range of files are searched for the given string and when found, the line number and the contents of the line are displayed.



• U2CPM.C - This C program scans through text file and converts all the line endings to the CPM standard of CRLF. This works for files edited on Mac, Linux, or Windows. It also adds a ^Z to the end of the file to conform with the CPM text file standard. This utility really helps clean up imported files that have been edited on foreign systems. Most of the CPM compilers and assemblers are quite picky on the line endings used in their input source files. This file compiles using BDS C 1.6.



• KERMIT - This is one of the classic programs used to communicate between assorted computers. I use this program daily to pass files between my linux box running ckermit in server mode and my FPGA_Z80 board. The program uses the CPM console (typically a USB serial port on P12) for user interaction and a second serial port (CPM AUX:) that is running on my repurposed printer port connector for streaming the kermit data to the host. This is a big complicated program, but I pretty much just use the "SEND" and "GET" commands. I did not do any significant modifications to the code but wanted it archived here as a working example. see the file KERMIT.TXT for instructions on configuring and building from source. You will need lasm and mload to assemble and generate the .com file for this package.



• XMODEM 2.7 - This is another of the classic programs used to communicate between assorted computers. The program uses the CPM console (typically a USB serial port on P12) for user interaction and a second serial port that is running on my repurposed printer port connector for streaming the xmodem data to the host. I did not do any modifications to the code as I was able to setup the wanted serial configuration in the XMODEM.CFG file.



• LS - An alternate disk file listing utility. It is similar to the CPM command "DIR", but I have it configured to list 3 columns of sorted file names with the details on each file including filename, size in bytes, user area on disk and the file attributes (like [sys]). I typically use it if I am trying to find a file on the disk and I dont know the user area. The stock "dir" command just lists non system files in the current user area, while this "ls" command lists all the files on the current disk.



• LIFE.C - A simple version of John Conways game of life converted to compile using BDS C 1.6 and run on a VT100 compatible terminal. This version just creates random initial cells and runs them through multiple mutations. Serial terminals kind of suck for graphics displays, but in its time this was mesmerizing to watch. A good screen saver display to use in the background while you are on a zoom call.

Source Code