David Griffith P112 Assembly And Operation Manual
P112 Single Board Computer
Assembly and Operation Manual
Revision 1.1
David Griffith
Wednesday May 10, 2006
1
This page is intentionally left blank.
2
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
3
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
4
10 Software 47
10.1 Z System and ZSDOS . . . . . . . . . . . . . . . . . . . . . . . . 47
10.2 Flash Programmer . . . . . . . . . . . . . . . . . . . . . . . . . . 48
10.3 DISKCOPY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
11 Warranty, Etc. 49
5
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 comp onents preinstalled for about a year, then stopped due
to lack of demand. Since then, the P112 has gained a reputation as a welldesigned 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 photographs 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.
6
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 reading) and lots of other goodies like more utilities, operating systems, languages, 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 electronics 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 components. 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 s older, but is more expe nsive. 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
7
particularly imp ortant. Just make sure it’s okay for electronics use and
you have the correct flux rem over. 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 mo dem 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.
8
2 Cables and Components
9 8 7 6 5 4 3 2 1
1
2
3
4
5
6
7
8
9
Serial connector wired straight through (solder side view).
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 c onnected 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:
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.
9
If you want to eliminate the need for an external null modem adapter, unscrew
9 8 7 6 5 4 3 2 1
1
8
972 345
6
Serial connector with null modem crossovers (solder side view).
the jack screws and rewire the pigtail as follows:
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.
10
2.2 Complete List of Parts
Capacitors Qty. Markings Location
22ρF ceramic 4 220k (blue) C1 C2 C25 C26
120ρF ceramic 1 121 J5A (blue) C12
.1µF bypass 14 104 CSR (tan) C3 C15 C16 C17 C18
C19 C20 C21 C22 C23
C24 C28 C29 C30
1µF, 16V tantalum 9 1 C4 C5 C6 C7 C8
C9 C10 C11 C27
22µF, 10V tantalum 2 22µ C13 C14
Resistor Packs Qty. Markings Locations
7x220 Ω
7x2.2k Ω 1 8A222G U14
7x47k Ω 2 8A473G U16 U17
Resistors Qty. Markings Location
4.7k Ω 3 yellow-violet-red R3 R4 R11
10k Ω 3 brown-black-orange R5 R7 R10
27k Ω 1 red-violet-orange R9
47k Ω 6 yellow-violet-orange R1 R2 R6 R8 R12
Semiconductors Qty. Location
74hct00 1 U5
74act02 1 U8
74act139 1 U11
DS1302 (RTC chip) 1 U6
TL7705ACP (TI reset gen.) 1 U15
LT1133 (RS232 tx/rx) 2 U7 U10
62256 (Static RAM, 32kb) 2 U2 U3
29c256 (Flash ROM, 32kb) 1 U4
1 8A221G U13
R13
Crystals Qty. Location
16MHz (CPU Clock) 1 Y1
32.768kHz (RTC crystal) 1 Y2
24MHz (IO chip clock) 1 Y3
Pre-installed Parts Qty. Location
BAR43C (diode) 1 D1
BAR43 (diode) 1 D2
BCW71 (transistor) 1 Q1
Z8018216FSC (CPU) 1 U1
FDC37C665IR (IO combo) 1 U9
11
Headers Qty. Location
2 pins 2 P5 P11
3 pins P1 P12 P13
5 pins 2 P2 P6
2x2 pins (4 pins) 1 P3
2x5 pins (10 pins) 2 P4 P8
2x10 pins (20 pins) 1 P14
2x13 pins (26 pins) 1 P7
2x17 pins (34 pins) 2 P9 P10
1x3 and 1x1 together 1 P1
The header at P1 is a T-shaped header made from a 1x3 strip and a single pin
by itself. To make things easier, it can be held together with a jumper block
while soldering.
Sockets Qty. Location
DIN48 expansion (white) 1 J1
8-pin DIP 2 U6 U15
14-pin DIP 2 U5 U8
16-pin DIP 1 U11
24-pin DIP 2 U7 U10
32-pin DIP 3 U2 U3 U4
20mm button cell holder 1 B1
Misc Parts
Qty. Location
Jumper block 10
#2032 lithium coin cell 1 B1
Chassis mount serial cable 2 P4 P8
Not included Qty. Location
NMF0512S (5/12V converter) 1 U12
The 5/12V converter is not included because flash ROMs that require 12 volts
for programming are now quite rare and this part is quite expensive.
12
3 Construction
3.1 Before Anything Else
Before you do anything else, please take the time to completely go through this
manual. Done? Okay, let’s begin.
3.2 Getting Started
It’s a good idea to have a few paper plates or bowls handy for spreading parts
out while keeping them neatly coralled and organized. Beware that you’ll be
playing with small shiny things. Cats like small shiny things, so make sure cats
can’t get to your workspace. It’s also extremely important that you do all this
on an anti-static surface.
Put on your grounding strap. Open the clear ziplock bag and empty it into a
plate or b owl. Check the list of parts in section 2.2 and make sure what’s listed
there is what you have in the bowl. Now open the grey bag and pull out the
printed circuit board and the slab of foam with chips and sockets embedded in
it. Check those parts against the list of parts too.
The colored bands on resistors are read with the gold band to the right. That
band indicates that these are 10% tolerance parts. The ceramic capacitors are
very easy to distinguish from one another. There is only one 120ρ unit. It’s
blue, and the value is written on the piece of tape holding its leads together.
There are a lot of bypass capacitors all wrapped up in a bouquet. The 22ρ units
are taped together side by side with clear tape and resemble match heads.
Tantalum capacitors are a bit more difficult. The 22µ units are usually larger
and often have their leads bent out to more easily fit in their holes. The 1µ
units look a bit skinnier and probably don’t have bent out leads. Check the
tantalum capacitors with a magnifying glass to make sure you know which is
which. Seperate them and/or mark them with a piece of tape. The positive
lead on the tantalums is marked with a tiny “+”.
Your kit may be supplied with tantalum capacitors marked differently than
above. These have colored bands instead of printing. A 1µ will be pink near the
legs and up about halfway. Then comes a band of black, then a band of brown.
On one side, there’s a white splotch. Hold the capacitor with the leads down
and the splotch facing you. The positive lead is the one on the right. Tantalum
capacitors have been known to heat up, melt, glow, burn things, belch clouds of
smoke, change colors, and stink (among other things) when mounted the wrong
way round.
Now it’s time to turn on your soldering iron. Make sure the tip is clean and
tinned (consult the iron’s manual).
13
I’ll assume you know how to solder. Remember that this is not a raw beginner’s
project.
3.3 Soldering the First Parts
RTC Crystal
Solder the low-lying parts first. Since we’ll mount the resistors on edge, the
chip sockets look like the logical choice. Don’t do that yet. We’ll start with the
RTC clock c rystal (Y2). This part is the size of a cooked grain of rice and is
hot-glued into a fold of heavy paper. Notice the rectangle extending from its
mounting holes. The crystal will lie parallel to the board in this area. Solder
the crystal into its holes leaving enough of the leads above board to let you bend
it down into the rectangle. Put a dab of epoxy or silicone RTV adhesive in that
rectangle and gently press the crystal into it. Let this cure before proceeding.
Chip Sockets
The sockets for U2, U3, and U4 appear to be of the press-fit variety. This isn’t
a problem as long as you don’t want to remove it after putting it in its holes.
Firmly, but gently press them into place and solder as usual. For the other
sockets, tape them down with some masking tape before flipping the board over
to solder them. If you’re brave you can use a finger and tack-solder the corners.
3.4 Soldering Everything Else
Capacitors
Our next-tallest components are the capacitors. Remember that the tantalums
are polarized. A magnifying glass or loupe is strongly recommended to check
for the tiny “+” mark. Look at the rectangle silkscreened around each capacitor. The positive lead of a polarized capacitor goes in the tapered end of the
rectangle.
Resistor Packs
These are also polarized. Hold the part with the lettering facing up. There’s a
dot on the leftmost pin. That’s pin one and it goes in the pin surrounded by a
square.
14
Discrete Resistors
To save space, the P112 board was designed to have its discrete resistors mounted
vertically. Hold a resistor with the gold band facing down. Bend the top lead
over so it’s parallel to the lower one. Mount the resistor with its body in the
circle silkscreened in its footprint. This leaves the part carrying the active signal
easily accesable at the top. Actually, it doesn’t matter which end gets bent over
which. I just like to put the gold end down so it’s easier to read the bands when
the resistor is mounted.
R5 somehow didn’t get a circle in its footprint. This resistor is connected to the
battery and it doesn’t matter which hole the body is mounted over.
Headers
Tape these down before soldering them. If you’re brave, you can hold them in
with a finger and tack down the ends. One header (P1) is made up of a single
row of three pins and a single pin. While soldering, put a jumper block on this
to hold it together.
Tall Crystals
There’s nothing special about these. Just make sure you put each crystal where
it needs to go.
Battery Holder
A holder for a #2032 lithium coin cell was substituted for the 1/2AA cell originally specified. If you want to use a 1/2AA cell as Dave Brooks did for the 1996
run of boards, you can do that. The holes for that are still present.
While it’s probably not necessary, a dab of epoxy or silicone RTV can be put
on the bottom of the battery holder to better secure it.
The height of this battery holder may interfere with mounting an expansion
board later. Then again, other things like Y1, P14, and jumper blocks will also
present a challenge. Keep this in mind when deciding whether or not to glue
down the battery holder.
15
4 Setting Up
If you haven’t yet washed the board with flux solvent, do so now. That flux goo
isn’t just ugly, but it can corrode circuits if left there. This is especially true if
you used paste flux.
Take a break. It’s best if you continue tomorrow. Don’t let yourself get too
anxious to get this board running. Rest your mind and body and you’ll be less
likely to do something stupid later on.
With the board assembled, basic tests may begin with the “obvious” checks for
Vdd-Ground shorts, etc.
Connect power to the board using the provided power pigtail. Red is positive.
Black is ground. Green is reset. Ground that wire and the board will do a
warm restart. Turn the power on and let it sit there for a couple minutes. If
anything smokes or makes a bad smell, go back and check polarities, espec ially
the tantalum capacitors.
Install the two SRAM chips in U2 and U3, and the flash ROM in U4. This kit
comes with 28-pin parts. The sockets are 32-pin to allow one to install larger
SRAMs and ROMs. Make sure you install these chips with their bottom ends
flush with the bottom ends of the sockets. If mounted with their tops flush, you
probably won’t let out the Magic Smoke, but it definitely will not work correctly,
if at all.
Install the rest of the chips and insert the lithium battery into its holder. Pay
close attention to the alignment notches. Chips mounted backwards will usually
get very hot and fail.
4.1 Jumper Settings
The jumper settings shown in the drawing below are for the default configuration
with 64kB RAM installed. Initially, it is recommended that jumper P11 be left
off so that the battery is isolated. This jumper is required when the real-time
clock chip and NVRAM is in use (which is most of the time). The jumper may
be removed in order to blank the NVRAM contents. If the P112 board will be
unused for a long period of time, the battery itself should be removed to avoid
the possibility of leakage. See section 9 for alternative jumper settings and their
purposes.
16
Loading...