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This is what is left of my love affair with the Z80. The page is presented as is, and no user support is available.

PBUFF was a printer buffer that could be configured from 8K to 4Mb of DRAM. Hardware Interfacing was done with only a single 74LS00 and a 74LS04. The magic was achieved with software and no hardware multiplexing was used.

 Source code is included to prove that it was possible, and yes, I am the only person I know that was able to do it. :-)

 The first set of 256K rams I saw, I got running in PBUFF, as I did with the 1Mb, and 4Mb types. I figured I didn't have to change the hardware until after 64Mb ram sizes.

 DRAM could be 1, 2, 4, or 8 DIP chips, or 30 pin Simm modules. I think I had 11 memory sizes.

 PBUFF started in approx. Nov-1984 and had about an 11 year run.

 ZLOAD was a development system based on PBUFF. It used a Jump ROM at address 0000H, that set the hardware and software jumps to 8000H. Your code was assembled for 8000H. At 8000H there was a battery backed RAM, so programming was simply done via a Printer port to this Ram. When the final program was achieved, it could be assembled for 0000H, and burnt into a ROM.

 This meant that EPROM Emulators were a thing of the past for Z80's. A simple board plugged into the EPROM socket of PBUFF to make ZLOAD functional.

 I also tuned an 8080 Tiny Basic program to work with my PBUFF board.

 An LED moving message board is also included, but circuits aren't available.

Download all files. 395K

Download PDF circuit for PBUFF. 97K

As stated above, none of the below is current information, or supported in any way.

UPDATED   1-Oct-1993(c)   (Orig Ver 1.0 20-Nov-84)


When I first advertised this kit in Jan. 85 it was a basic 8K to 64K buffer.
The 256K version was featured in Australian Electronics Monthly magazine in
Mar. 87 as the star project. The 1Mb version appeared in Silicon Chip
magazine in Oct. 89. The current Rev. K board has additional provision to
install an alternative 256K/1Mb/4Mb  SIPP/SIMM type MEMORY MODULE. That
means, you can either install standard 16 or 18 pin by 1 bit Drams, or a
MEMORY MODULE. Both 8 byte and 9 byte type MODULES can be used. The software
ignores the ninth byte.

PBUFF Supports a mixture of 64K/256K/1Mb/4Mb DIP/SIMM/SIPP DRAMs in 10
memory sizes up to 4Mb. Supports 64K, 128K, 256K, 320K, 512K, 1024K, 1088K,
1280K, 2048K, and 4096K (4Mb). Needs user wired 74LS139 decoder chip for
some intermediate memory sizes. Some memory sizes can be done with a
combination of standard Drams and a MEMORY MODULE. EG:- 512K can be done
using a set of 8 by 41256s and a 256K MEMORY MODULE. Standard assembly
instructions covers all memory size installations. This version increases
saturation loading time by more than 50 per cent over ealier versions. This
represents a load rate of over 300K per minute using a PC/AT as the host and
a 3.58mhz crystal in PBUFF. Instructions are given to increase the speed of
PBUFF to a possible 10Mhz clock frequency. This reflects a load rate of
around 900K per minute.

My "PBUFF" printer buffer kit sales now exceed 4000 units worldwide, which I
believe speaks for itself. These kits have a single/multiple copy facility,
Hexadecimal output mode, OPTIONAL hardware pause, DATA/STATUS LED, power
connector for SERIAL board expansion, and extensive ROM diagnostic routines
to aid kit builders.

This buffer installs in-line to your printer using standard centronics
signals. I have designed it so that it can be powered up with an existing +5
volt supply, or an external input voltage of 9 volts AC or DC. Any plug-pack
capable of supplying 400mA or more will suit this project. If a SERIAL board
is to be fitted, then a 9 volt @ 1 amp A/C supply must be used.

PBUFF also supports the C3P1 and FPIO (front panel input/output) boards. It
has kit builder diagnostics which includes static ram test, 555 timer test,
printer test before Drams are installed, and individual DRAM fault checking.
A respectable Hex dump format is provided. This complies to a normal utility
type format of ADDRESS, HEX data, and ASCII data in three separate columns,
with auto flush of the last block of data when the computer goes to sleep
for eight seconds, and a last byte in file indicator. It auto senses the
DRAM type and sets it's routines accordingly.

I am selling this unit in what I call a "PBUFF SHORT FORM KIT". This
consists of:- One bare double sided plated through printed circuit board.
One EPROM programmed with PBUFF Ver 5.1E. Full assembly instructions,
includes circuit, operator instructions, the memory doubler circuit details,
and hardware debugging section. All text is supplied on an MS-DOS format
3.5" floppy. This includes a test program that will verify the memory size
and load rate of your buffer, plus the current ROM file as a backup.

You provide all other parts and labour. You must have in your tool kit a
multi-meter, and if you do run into real trouble, a Logic Probe may be

Check my ORDER FORM for the current price of the PBUFF SHORT FORM KIT. How
much are you really up for? You have to provide a suitable case, power-pack,
(or transformer) centronics connectors and cables, plus approx. $30-$40
worth of additional components, plus your memory chips. If you are a
hardware hacker like me, you already have most of the components.

The printed circuit board has been designed to mount straight into the DICK
SMITH Instrument case, CAT H-2505 PBUFF accepts from 64K up to 4Mb of
characters from a centronics printer port, and stores it until your printer
has completed it's task. This releases your computer for other work.

PBUFF is running on all types of computers from the early TRS-80's and
Apples to the latest IBM PC/XT/AT/386/486 and compatible clones, Amiga,
Macintosh Plus, Microbees, VZ200/300, Tandy Color (using serial board
addition), In fact we have yet to find a true CENTRONICS port that it
doesn't run off.

Connector J1 on the PBUFF board is an extension of the Z80 chip pinout and
is used for connection to FPIO & C3P1 boards, or user prototype boards. A 40
pin dual row male header can be soldered into this position.

The cheapest printer cable that you can buy today is an IBM type DB25 to 36
pin Centronics. The PBUFF board makes use of IBM cables and standard
connectors to save cost and simplify construction of cable interfacing.
Headers are also provided for IBM standard flat ribbon cable pinout so that
the unit can easily be installed inside a desktop if required.

The input and output wiring has now been taken care of on the main PBUFF
board. Older boards had a separate Back Panel I/O board. This was known as
the BPIO board. Reference may still be given to this board on some of my
other assembly instructions. What I have really done is to join the artwork
of my PBUFF board to the BPIO board so that it becomes one board, and
included the electrical connections in the artwork to save on header and
connector costs. Header J2 connects pin for pin to header J7. If isolation
is required for Serial or other switch boards, the tracks must be cut
between the points marked "A" and "A" on the component side of the board.
This bus is called the PBUFF I/O bus. To re-connect this bus for any reason,
26 pin male headers can be soldered into the J2 and J7 positions, and a
short length of 26 wire flat ribbon cable that has two IDC crimp headers
attached to either end can be inserted onto the male header pins.

Z8TBASIC (Z80 TINYBASIC) Version 2.0 by Don McKENZIE  UPDATED 29-August-93(c) NOTE *** This is a short version of the file contained in {ZBASIC}.ZIP *************************************************************************** Z8TBASIC get up and go instructions, for impatient types like me... To get Z8TBASIC running from a standard ZLOAD Version 2.0, and burn results to an EPROM only, Basic Interpreter operating system, do the following: (1)  Make 3 wire DB-25M dummy plug as described in text, insert into DB-25F. (2)  Set Load Mode, press Reset. (Led flashes 5 times.) (3)  COPY ZBAS2RAM.HEX LPT1: (This copies Basic Interpreter to ZLOAD).      After Load, Led continues permanent flash at a fast rate. (4)  Press and hold Reset, switch to Run mode, release Reset. If Front Panel      I/O is fitted, Version Number 2.0 will be displayed. (5)  Run FEND.COM. Video should print PBUFF Ready>_ (6)  LOAD GIG (Will Auto-Run. This is a Gigabyte counter.) (7)  Press F1, Toggle Move on, Esc. (This patches Add 4 in CURRENT.ROM) (8)  Break program with ^C, (Edit if required,) SAVE MYPROG and Esc to DOS.      This creates and updates Rom image file. (9)  Burn 2764 from file CURRENT.ROM (10) Remove ZLOAD EPROM, insert your new MYPROG Basic EPROM. (11) Set to LOAD position, and the Basic Program will run from the EPROM.      Read on.... *************************************************************************** Z8TBASIC (Z80 TINYBASIC) Version 2.0 by Don McKENZIE  UPDATED 29-August-93(c) Re-assembled for operation with ZLOAD Version 2.0 Read Zload text files for full information on these changes. Once again, I have changed Zload to PC write routine. Video still gave occasional errors. ------------------------------------------------------------------------------- Z8TBASIC (Z80 TINYBASIC) Version 1.1 by Don McKENZIE  UPDATED 30-July-92(c) Changed Zload to PC write routine. Video gave occasional errors. I recommend that Z8TBASIC be run in communication mode from a PC at a ZLOAD speed no greater than 6.144MHz. That is, ZLOAD running at 6.144Mhz. Stand-alone Z8TBASIC will run at much faster speeds. To date, Z8TBASIC has been tested on PC's from 6Mhz 286's to 33Mhz 386's. ------------------------------------------------------------------------------- Z8TBASIC (Z80 TINYBASIC) Version 1.0 by Don McKENZIE  UPDATED 13-May-92(c) Program a stand alone Micro-controller with BASIC. A standard IBM PC Parallel Printer port is used during development. SOFTWARE OVERVIEW.... Z8TBASIC is an Integer BASIC Language interpreter that runs on my ZLOAD Z80 development kit boards. This can be in an EPROM, or downloaded to a Static Ram. FEND.COM runs on an IBM PC and is the Front-End program for Z8TBASIC. This handles Keyboard, Video, and Disk I/O. These two files allow you to use a PC as a terminal for a BASIC Language micro-controller development system. Upon completion of program development, you will be able to burn an EPROM to run a PBUFF board as a Micro-controller in BASIC.                                           &nb;          HARDWARE OVERVIEW.... A standard ZLOAD Version 2.0 board is connected via a standard Parallel printer cable to LPT1 of an IBM PC. This is the communication path for Keyboard, Video, and Disk I/O. Instead of connecting a Printer to the DB25 female output of PBUFF, a dummy DB25 male plug is connected. This dummy plug must have the following three jumpers installed: Pin 2 to pin 14 (Data), pin 3 to pin 16 (toggle Strobe), and pin 10 to pin 17 (Ack). These three jumpers connect the signals that are the data path from PBUFF to the PC. IE: Video out and Disk writes. The standard data path from the PC to PBUFF has been retained so that file dumps (COPY /B FILENAME.EXT LPT1:) can be done. This is also the data path for Keyboard data, and Disk reads. Upon completion of program development, you can software disable Keyboard, Video, and Disk I/O, and remove the printer cable and dummy plug. *************************************************************************** GENERAL OVERVIEW.... Z8TBASIC can only be used on Revision H (Feb-89) or later PBUFF boards. PBUFF was developed by me as an 8K to 64K printer buffer kit in Dec-84, and has appeared in several Electronic magazines as a project. It now supports 4Mb as a printer buffer. It is the heart of my message board and other projects. ZLOAD Version 1.0 was originally a PBUFF board and a small satellite board that had provision for a battery backed Static Ram that could be switched to address zero in place of the EPROM. It also had a 74LS74 and a 74LS32 that were used to flip these 28 pin devices and write protect the static ram. It also had two status LEDs. It was designed as a Z80 Machine Language Development System. I have now done away with this satellite board and replaced it with software. So now, PBUFF and ZLOAD are one and the same, the only difference being the EPROM firmware, and I have overcome this restriction by using a 27128 EPROM to do both jobs. See my ZLOAD instructions for more details.
ZLOAD Version 2.0  A NEW POWERFUL Z80 MICRO DEVELOPMENT TOOL by Don McKENZIE Updated 1-Oct-93. First Released 1-Oct-93(c)        (Orig Ver 1.0 20-Jan-90) Professional software development of micro-controllers is an expensive business that could demand the purchase of some very sophisticated electronic equipment such as micro in circuit emulators (MICE) that would set you back in the neighborhood of several thousands of dollars to less expensive EPROM emulators that cost around $200 to $500. Or perhaps on a hobbyist level, you would like to make your own simple low cost controller for security systems, robots, in line code translators, household appliances, lighting displays, video and audio switching networks, model railways, sporting event timers or flip vane displays. Well, this project should suit anyone interested in Z80 controller development. BASIC DESCRIPTION...... ZLOAD is a Z80 development tool used to accept a super fast down load of Z80 machine code from the Centronics printer port of an MS-DOS PC. Output is directed to a PBUFF (my Printer Buffer) CPU board which is used as the target microcontroller development system. The static Ram of PBUFF can be very easily battery backed up if desired. The file can be a "ROM" type binary file or in IntelHex format. EPROM burning is not required during development as ZLOAD emulates an EPROM. An 8K file will load in under 3 seconds on a standard 4.77Mhz PC. The command to direct a file from disk to your line printer port is "COPY /B FILENAME.EXT LPT1". The /B option is used for a binary load. If it was not used, the file copy would abort when the first ^Z (1AH) was detected. If you order a "PBUFF" Printer Buffer short form kit, you also get a "ZLOAD" Z80 Micro Development system short form kit, and if you order a Z80 Micro Development system kit, you also get a Printer Buffer kit. WHY? Because they are now one and the same, and so is the price. The board also supports up to 4Mb of Dynamic Ram data storage. Full Source code supplied. I have simplified the construction of ZLOAD by doing away with the extra hardware that my old Version 1.0 used. The tradeoff is a small amount of software manipulation that is easily understood and implemented. Code is assembled at 8000H for Emulation mode or Zero for your final EPROM version. A parallel printer port to Static RAM loader is in the lower half of the ZLOAD EPROM. This is the LOAD mode. The upper half of the EPROM has a Jump Rom. This is the Run mode, which re-directs all Power-up, Reset, and Restart hardware and software sequences from the standard Z80 Base addresses to the Static Ram at 8000H, which is where the loader puts your code. The Load/Run mode is selected using a switch connected to the J6 header pins. Instead of supplying the software in an 8K EPROM, I supply both PBUFF and ZLOAD in a 16K EPROM which is default set for use as a PBUFF Printer Buffer. I have taken the liberty of reducing the price of ZLOAD and supplying a USED 27128. But I don't guarantee it is used. You may end up with a new one. The supplied 3.5" 720K disk contains ALL Source Code listings and ROM dumps including PBUFF, ZLOAD, my moving Message board version 1.1C, and lots more. A collection of circuits and assembly instructions have been included in the package that should greatly assist Z80 hardware designers. Z8T.COM, a public domain 8088 program is now supplied with ZLOAD. This is all you need to assemble Z80 code, and it's fast. You can forget the other methods. I have used only ZLOAD and Z8T.COM for all of my Z80 development for four years now. The technique can be easily adapted to other systems. And on top of all of that you get Z8TBASIC, an integer Basic Interpreter that runs on my PBUFF boards. It's simple, but it works, and allows you to write and develop controller programs in Basic using your PC. After final de-bugging, your program and Basic Interpreter is burnt into a 2764 EPROM.
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