David Griffith P112 Installation and operating instructions

P112 Single Board Computer
Assembly and Operation Manual
Revision 1.1
David Griffith
Wednesday May 10, 2006
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Contents
1 Introduction 4
1.1 What is this thing? .......................... 4
1.2 What do I need to know? ...................... 4
1.3 What’s in this kit? .......................... 4
1.4 What’s not in this kit? ........................ 5
2 Cables and Components 7
2.1 Cables ................................. 7
2.1.1 Power Cable ......................... 7
2.1.2 Terminal Cable ........................ 7
2.1.3 Disk Drive Cable ....................... 8
2.1.4 Parallel Port Cable ...................... 8
2.2 Complete List of Parts ........................ 9
3 Construction 11
3.1 Before Anything Else ......................... 11
3.2 Getting Started ............................ 11
3.3 Soldering the First Parts ....................... 12
3.4 Soldering Everything Else ...................... 12
4 Setting Up 14
4.1 Jumper Settings ........................... 14
4.2 Terminal Settings ........................... 15
4.3 Disk Drives .............................. 15
4.4 Powering Up ............................. 16
5 Debugger 18
5.1 Help Function ............................. 18
5.2 Set Breakpoint ............................ 19
5.3 Display / Set Memory ........................ 19
5.4 Go (Run Program) .......................... 20
5.5 Trace instructions .......................... 20
5.6 Display / Set Registers ........................ 21
5.7 Loading Files ............................. 21
5.8 Input from Port ............................ 22
5.9 Output to Port ............................ 22
5.10 System Boot ............................. 22
5.11 Load OS and return to DEBUG .................. 22
5.12 DS-1302 RAM Parameters ...................... 23
6 Troubleshooting 25
6.1 Stone Dead .............................. 25
6.2 Garbaged Sign-on Message ..................... 25
6.3 Disk Drive Won’t Work ....................... 25
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6.4 An Example .............................. 27
7 Logic Description 28
7.1 CPU .................................. 28
7.1.1 Serial Port .......................... 28
7.1.2 Parallel Port ......................... 29
7.1.3 DMA ............................. 29
7.1.4 Memory Mapping ...................... 29
7.2 Memory ................................ 30
7.2.1 ROM ............................. 30
7.2.2 On-Board RAM ....................... 31
7.2.3 Expansion RAM ....................... 31
7.3 IO Cycle Control ........................... 31
7.4 Real-Time Clock ........................... 31
7.5 Expansion Socket ........................... 32
7.6 Multi-I/O Chip ............................ 32
7.6.1 Address Decoding ...................... 32
7.6.2 Cycle Timing ......................... 32
7.6.3 Safety Latch ......................... 32
7.7 Serial Port 2 ............................. 33
7.8 Diskette Port ............................. 33
7.9 Printer Port .............................. 33
8 Major Components 34
8.1 CPU Chip ............................... 34
8.2 I/O Combination ........................... 34
8.2.1 Port Addressing ....................... 34
8.3 Flash ROM .............................. 35
8.4 Realtime Clock ............................ 35
9 Connector Pins 36
9.1 P1 — RAM Size Selector ...................... 36
9.2 P2 — DMA Requests ........................ 36
9.3 P3 — Flash Bootload Selector .................... 36
9.4 P4 — Serial Port 1 .......................... 38
9.5 P5 — SYNC Jumper ......................... 38
9.6 P6 — Power Supply / Reset ..................... 39
9.7 P7 — Parallel Printer ........................ 39
9.8 P8 — Serial Port 2 .......................... 40
9.9 P9 — Disk Drives 0 and 1 ...................... 41
9.10 P10 — Disk Drives 2 and 3 ..................... 41
9.11 P11 – Battery Isolator ........................ 41
9.12 P12 — ROM Pin-3 Function .................... 42
9.13 P13 — RAM Pin-30 Function .................... 42
9.14 P14 — Extra Serial Ports ...................... 42
9.15 J1 — Bus Expansion ......................... 45
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10 Software 47
10.1 Z System and ZSDOS ........................ 47
10.2 Flash Programmer .......................... 48
10.3 DISKCOPY .............................. 48
11 Warranty, Etc. 49
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1 Introduction
1.1 What is this thing?
This document provides detailed illustrated instructions on building and using
the P112 single board computer. This board has the footprint of a typical 3.5”
floppy drive and may be mounted on the underside of one. Its CPU is a Zilog
Z180 (an enhanced version of the venerable Z80). A multifunction I/O chip
provides serial ports, a parallel port, and support for up to four floppy drives.
A terminal, or at least a null-modem cable connected to another computer
running a terminal-emulator is required to communicate with the P112.
The P112 was designed by David Brooks in 1996. He sold boards with the
five surface-mount components preinstalled for about a year, then stopped due
to lack of demand. Since then, the P112 has gained a reputation as a well-
designed machine for running CP/M and similar operating systems. In late
2004, in response to growing interest in the P112 board, another run of boards
was produced by David Griffith. After a lot of work, unexpected problems, and
gnashing of teeth, kits started to ship in late 2005.
Most of the content of this manual is taken directly and usually verbatim from
two PDF files produced by David Brooks in 1996 as documentation for the first
run of P112 boards. Other content comes from documentation from related
utilities written specifically for the P112.
This introduction, assembly instructions, software documentation, and pho-
tographs were created by David Griffith.
1.2 What do I need to know?
You should know the basics of soldering. Because of the small size of this board
and certain delicate parts, I do not reccomend this as for a first soldering project.
Get a little project kit from Jameco and practice there first.
1.3 What’s in this kit?
In this kit you will find the following:
One four-layer printed circuit board
A four-layer circuit board is not something one can easily make in the
garage. This board has two surface-mount chips (the CPU and the IO
controller) and some discrete devices already mounted. Since there was
no way around having those surface-mount parts, that part has been done
for you.
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One set of electronic components
All the hard work of finding these components at good prices has already
been done for you.
One 3.5” floppy disk
This is a ZSDOS boot disk created by Terry Gulczynski specifically for
this new run of P112 boards. The boot disk supplied by David Brooks
with the first run of P112 boards will still work, but is discouraged.
One copy of the Walnut Creek CP/M CDROM
This CD dated November 1994 contains assorted utilities, games, system
software, source code, and other things for computers running CP/M or
similar operating systems. It has long been out of print and Walnut Creek
has said that no permission is needed to reproduce it.
One documentation CDROM
This CD contains the new P112 documentation (which you are now read-
ing) and lots of other goodies like more utilities, operating systems, lan-
guages, and so on. A lot of stuff gathered by Rlee Peters is also included.
This CD is not documented in this manual.
1.4 What’s not in this kit?
This kit doesn’t include things that can be found at a typical consumer elec-
tronics parts shop. Other things you might want to complete this project can
be easily found on auction websites like Ebay. You might also have much of
these things already.
Soldering equipment All of these soldering items can be found at Radio
Shack (http://www.radioshack.com/).
A soldering iron drawing 15 to 30 watts is plenty powerful for this job.
Don’t go any higher or else you’ll risk damage to the board and/or compo-
nents. Make sure you have a narrow tip. One of those cylindrical tips that
you sharpen to a point with a file will work, but will be very frustrating
to use when mounting the expansion connector.
Plain old 60/40 solder of .032” or .064” (.6mm to 1.2mm) is good. If you
prefer 63/37, that’s good too. Make sure you get rosin-core solder. Acid
core solder will ruin electronics. A solder of 96% tin and 4% silver is a
good choice of lead-free solder, but is more expensive. Two ounces (about
50 grams) of solder will be plenty.
It may be necessary to flux the board. I needed it. Others have reported
that it’s not necessary. You’ll know if you need it if molten solder will
not wet the connection you’re trying to solder. The type of flux is not
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particularly important. Just make sure it’s okay for electronics use and
you have the correct flux remover. Radio Shack stocks suitable paste flux
and flux remover.
Picks, tweezers, and brushes will be handy.
Desoldering braid is essential for cleaning up mistakes. Don’t fool yourself
into thinking you won’t make any mistakes.
Grounding strap This is also available at Radio Shack. This device is essen-
tial to prevent static electricity damage to chips.
Chip puller and inserter This is also available at Radio Shack. They are
frequently included in “computer tool kits”.
Chip pin straightener You may or may not need one, but it’s a good idea to
have one just in case. They sometimes can be found at Radio Shack. The
Jameco part number is #99362. Mouser doesn’t appear to carry it.
Serial terminal You’ll need some way to talk to your new computer. A
second-hand dumb terminal found on Ebay (http://www.ebay.com) will
serve you well. Make sure you also get the correct cables. A null modem
adapter may be necessary.
Null modem cable or null modem adapter If you can’t get a terminal,
you can use a null modem cable and a terminal emulator program.
Floppy drives You’ll need at least one floppy drive. Two is nicer. You can
have as many as four, but two drives is best. This board can use any
internal 34-pin-interface floppy drive that an x86 PC can. Purists might
want to use 5.25” drives. 5.25” disks can be a bit hard to find, but it
shouldn’t be a big problem. Since this kit includes only 3.5” disks, use
3.5” drives unless you know what you’re doing. If you really know what
you’re doing and know where to look, you can use those big 8” floppies.
Chassis You’ll probably want a case to put your computer in when you’re
finished. Radio Shack carries a small variety of cases that might suit you.
A better choice may be to get an old external hard drive case.
Power supply This computer draws about 150 milliamps not including the
floppy drives. Even the tiniest computer power supply should work fine.
If you mount your computer in an old hard drive case, chances are that
you’ll have a good power supply too.
Mounting hardware and tools I can’t anticipate what situations that may
arise when mounting your computer. A computer shop or Radio Shack
will be helpful. You’ll have to look at how you want to mount the board
and what you’ll need to do it. If you want to mount it to the underside
of a floppy drive, you’ll need some standoffs and screws.
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2 Cables and Components
2.1 Cables
All the basic I/O connections are at the left edge of the PCB. You will need the
following cables to run the board:
2.1.1 Power Cable
Connects to P6. Reading from top to bottom the pins are
GND
VDD
Reset
VDD
GND
The Reset pin may be left unconnected (it has a pull-up). To force a reset, pull
this line low.
Nominal power consumption (PCB only) is 150mA at 5V.
2.1.2 Terminal Cable
RS-232 terminals may be connected to P4 and P8 with the primary terminal
being at P4. A 10-conductor ribbon cable connects via a standard IDC socket
to the board. The tenth conductor is clipped off and the rest are crimped or
soldered to a standard IDC DB-9 plug as follows:
987654321
1
2
3
4
5
6
7
8
9
Serial connector wired straight through (solder side view).
This generates the same pinout as a 9-pin serial port found on a typical x86 PC.
Two cables wired like this have been provided in your kit of parts. Depending
on how your terminal’s serial port is wired, you may need a null modem cable
or adapter.
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If you want to eliminate the need for an external null modem adapter, unscrew
the jack screws and rewire the pigtail as follows:
987654321
1
8
9
7
2 3
4
5
6
Serial connector with null modem crossovers (solder side view).
This will allow you to connect the P112 to an x86-style serial port with a cable
wired straight through. Again, depending on your terminal, you may be able
to use a standard 9-to-25-pin modem cable to connect the P112 to a standard
serial terminal.
2.1.3 Disk Drive Cable
This is wired as for a PC-AT, ie a direct 34-way connection from P9 or P10 to
the first drive, then cores 10-16 reversed in the path to the 2nd drive. In P9, the
first drive will be Drive 0, and the second Drive 1. From P10, they are Drives
3 and 2 similarly (note the reversed assignment).
In other words, a standard floppy ribbon cable is what you need. This cable is
not included. Sorry, I couldn’t find enough in large quantities.
2.1.4 Parallel Port Cable
A standard 26-way IDC receptacle fits the board. Clip off core 26 of the cable,
and run the others to a DB-25 socket (Pin-1 to Pin-1). This generates a standard
PC-type printer interface.
This sort of cable is identical to the provided terminal cables. Unfortunately, I
was unable to find any of these pre-made, so one is not included in the kit of
parts.
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