Development system continues Z80 legacy

Development system continues Z80 legacy

Colin Holland

8/24/2010 8:32 AM EDT

The ZiLOG Z80 is a 8-bit microprocessor made and sold by ZiLOG from July 1976 and is one of the most popular microprocessors that a whole generation of electronics and programmers has grown up with. It found usage in desktop and embedded computers – a wide spectrum from game console up to military applications. The Z80 derivatives and clones make this CPU the most used processor of all times.
To face the obsolescence of Z80 development tools System TRAINZ (Erfurt, Germany) has come up with a simple form of  development system. During conception of System TRAINZ the key problem was to load a binary file (mostly this is Z80 machine code) into the RAM, test it and burn it into the on-board flash EEPROM.

The hardware of System TRAINZ.

System TRAINZ can be used software development (assembly, C, …), learning the basics of computer engineering, programming, repair and maintenance, control and measurement as well as the assembly and troubleshooting of complex electronics.
Use of ICs on sockets, through-hole technology and moderate clock frequencies of less than 11 MHz the user has a robust and easy to repair computer system. System TRAINZ can be operated in the targeted application without any modifications.
The system provides an RS232 interface to host computer, operation via terminal program running on host computer not dependent on any operation system of the host computer, hardware that can operate in the targeted application and testing of the user written program in the system RAM. The user written program is uploaded into the systems 32-kbyte flash EEPROM and is executed at system start.  An open system bus is provided for user made hardware extensions and I²C provides support for peripheral devices.
The user can change mountings of components, to make customize the configurations of both hardware and software.
It does not include Z80 assembler, compiler or interpreter software, or provide single step program execution, debugging functions, breakpoints or  video interfaces such as VGA or FBAS
This module can be used with any computer that is equipped with a serial RS232 interface and a terminal program. So System TRAINZ can be operated with Linux, UNIX, MSDOS and MSWindows. Terminal programs of these operating systems are for example Minicom or HyperTerminal.
The physical assembly consists of two EuroBoards (100 x 160 mm), the main board
and the memory board memory management unit (MMU).

Main board layout.

On the host computer a terminal program is required. Users running Linux may use
Minicom, under MSWindows
The parameters of the RS232 interface used to communicate with System TRAINZ are to be set somewhere within the terminal program and are:

data transfer rate 9600 bit/s,
8 bits per character,
no parity,
1 stop bit,
hardware flow control.

The data transfer rate can be increased to 19200 bit/s by doubling the frequency of the system clock. As a default every character received by System TRAINZ gets echoed back to the host
computer which makes the character visible on the screen. This allows the verification of the character sent by the host computer. In order to reduce the data traffic the echo can be disabled.
The communication of System TRAINZ with the host computer is designed to allow automated communication like scripting with Kermit.  The proper function of USB to RS232 adapters has not been tested in connection with System TRAINZ and the state of the CTS signal driven by the host computer is ignored since the host is assumed to be much faster than System TRAINZ.
The 10-MHz master clock generates oscillator QG1. By means of a frequency divider the master clock gets divided by 2, 4, 8 and 16. JP5 allows the selection of the desired system clock by plugging a jumper on it. Default setting is 2.5-MHz.  The frequency of the system clock directly affects the data rate of the serial interface as well as all other timings withing System TRAINZ. A system clock higher than 2.5-MHz can be run safely only if all components depending on it support this clock frequency.
Both channels A and B of the serial interface (SIO) can be used. System TRAINZ uses only channel A for the RS232. Transmit and receive clock of both channels is fed by the CTC unit. If System TRAINZ is to be operated in an electromagnetic harsh environment the line receivers  and   may be equipped with external capacitors in order to block noise from the lines RXD, CTS, DCD and RI.
The Z80 parallel input-output (PIO) has two ports. Port A is free for any usage. Exception is the system test. The logical state of signals A0 and A1 is displayed by the LEDs D0 and D1. Primarily port B controls both the I²Cbuses 0 and 1, the monitoring of the RI signals and the system start.
Minor hardware modifications by the user make port B free for any usage.

The MMU board.

System TRAINZ is assembled and delivered with these components:

Main board
MMU board
Two 40 pin ribbon cables
An adapter for serial interface RS232 without ferrit core 
An adapter for parallel interface 
32-kbyte flash EEPROM
32-kbyte SRAM.

As well as fully assembled boards, the two bare boards, MMU and MAIN, are avilable without any devices soldered on them.
The fully assembled board is €160 while the bar Main board and MMU board are €40 each.
For more information see the System TRAINZ website.