Acorn BBC Master 65C102 User manual

Within this publication the term 'BBC' is used as an abbreviation
for 'British Broadcasting Corporation'.
°Copyright ACORN Computers imited 1985
Neither the whole or any part of the information contained in, or
the product described in, this manual may be adapted or reproduced
in any material form except with the prior written approval of ACORN
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The product described in this manual and products for use with it,
are subject to continuous development and improvement. All
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are given by ACORN Computers in good faith. However, it is
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product and this manual.
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First published 1985
Published by ACORN Computers imited
Cover design concept by Carrods Graphic Design

65C102 co-processor user guide
Part No. 0443,030
Issue No.2
April 1986

CONTENTS
Section Page
INTRODUCTION 3
Dismantling the microcomputer 5
Installing the co-processor printed circuit board 5
SYSTEM MEMORY 9
The 65C102 co-processor support disc 11

INTRODUCTION
What is a co-processor
The job of the co-processor is to run languages such as BASIC,
assembly language, word processing, and to run user programs. The
TUBE handles the two-way communication between the microcomputer and
the co-processor thereby leaving the microcomputer and the co-
processor to continue with their respective tasks.
With the co-processor fitted, the job of the microcomputer is to
serve as an I/O processor, that is, to handle all the inputs and
outputs (keyboard, RS423, text and graphics output to monitors,
printer output, disc drives, cassette recorders, local area network
and so on).
This co-processor consists of a 65C102 microprocessor system with 64
Kbytes of Random Access Memory (RAM). In addition, it contains an
interface between itself and the microcomputer called the TUBE.
From this point on the microcomputer will be referred to as the
I/O processor.
Fitting a co-processor
Note that any modification or upgrade carried out to the printed
circuit board of any Acorn equipment is undertaken at the sole risk
of the person carrying out the modification or upgrade. No claim for
loss or damage to the equipment caused by the modification or
upgrade of the printed circuit board by unqualified personnel shall
be accepted by Acorn Computers limited.
WARNING - A number of the components used within ACORN equipment are
STATIC SENSITIVE. All usual anti-static precautions must be taken to
prevent damage to these devices.
Before attempting this upgrade, please read all the instructions
carefully. If you are in doubt about your ability to carry it out,
the co-processor and the microcomputer should be taken to your
nearest authorised Acorn dealer.
A charge may be levied by the dealer for installing the co-
processor; such a charge shall be entirely at the discretion of the
dealer concerned.
3

FIGURE 1
4

Dismantling the microcomputer
Before attempting to fit the co-processor to your machine, first
ensure that the unit is disconnected from the mains power supply.
The upper half of the case must be removed from the unit to allow
access to the main printed circuit board. To do this, turn the
computer upside down and place it on a firm, flat surface; locate
and remove the four fixing screws that hold the upper half of the
case in place. These screws are located on the underside of the unit,
two at the rear and two at the front of the machine, and are
labelled 'FIX'. Please note that the two fixing screws fitted to the
rear fixing positions are longer than the other two.
When the fixing screws have been removed, carefully re-invert the
computer whilst holding the two halves of the case together. The
upper half of the case may now be removed by lifting it directly
upwards from the machine.
Installing the co-processor printed circuit board
Included in the co-processor upgrade kit are a number of plastic
printed circuit board support posts. These must be fitted to the
main printed circuit board before installing the co-processor board.
The positions at which these posts are to be fitted are shown in
figure 1. The posts should be fitted to the positions in numerical
order. The first four positions are common to all co-processor
options, with positions five and six only in use with certain
co-processors. When fitting the P.C.B supports, ensure that the base
flange does not interfere with any component on the P.C.B. To fit
the support, insert one end into the hole in the P.C.B and press
down gently.
When the support is correctly fitted, it will not be possible to
withdraw it from the hole in the P.C.B. Care must therefore be taken
to ensure the correct positioning of the P.C.B support before
pressing it home.
When all the P.C.B supports are installed on the main P.C.B, the co-
processor should be placed in position ensuring that:
1. The pins of P 1 on the co-processor are aligned with the
corresponding holes in SKI on the main P.C.B.
2. The pins of P 2 on the co-processor are aligned with the
corresponding holes in SK2 on the main P.C.B.
3. The P.C.B supports are aligned with the corresponding holes on
the co-processor P.C.B.
When you are satisfied that all the pins and supports are correctly
aligned, the co-processor P.C.B may be pressed gently into place.
The co-processor is correctly seated when the barbs on the tip of
the P.C.B supports have cleared the surface of the co-processor
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P.C.B. An audible click should be heard when the barbs spring into
place securing the P.C.B.
Take care not to exert too much pressure when pressing home the co-
processor P.C.B, this may lead to damage to the various connectors.
When the co-processor P.C.B has been installed, the re-assembly
procedure is the reverse of the dismantling procedure.
When the 65C102 co-processor has been installed, the machine should
be set up as described in the WE COME GUIDE. When the machine is
switched on a message, similar to the following, should appear on
the screen.
ACORN MOS
ACORN ADFS
BASIC
>_
As can be seen from the above message, the 650102 co-processor does
not appear to be present. The reason for the apparent abscence of
the co-processor is the CONFIGURATION status of the machine.
To reconfigure the machine to allow for the inclusion of the 65C102
you must use either a *CONFIGURE command, or the control panel
included with the WE COME package. To use the *CONFIGURE command you
should enter:
*CONFIGURE TUBE <RETURN>
followed by
*CONFIGURE INTUBE <RETURN>
after entering these two commands you must perform a hard reset by
holding down the CTR key whilst pressing and releasing the BREAK
key. This reset is needed to enable the I/O processor to recognise
the presence of the co-processor.
After performing the reset, the following message, or something
similar, should be displayed:
ACORN TUBE 65C102 CO-PROCESSOR
ACORN ADFS
BASIC
>_
6

The top line of the display shows that the TUBE and 65C102 co-
processor are now recognised by the machine. If the message on your
machine does not indicate the presence of the 65C102 co-processor
then first use the *STATUS command to determine whether the TUBE is
correctly configured, and assuming that the configuration is correct,
refer to the ealier part of this section to check that the upgrade
has been carried out correctly.
If neither of these courses of action uncover the cause of the
problem, the complete machine should be taken to your nearest Acorn
registered dealer for testing and, if necessary, repair.
7

8

The *CONFIGURE command
The *CONFIGURE command may be used to enable and disable the TUBE
communications. It may also be used to select between internal and
external TUBE communication. To enable or disable the TUBE
communication, *CONFIGURE with TUBE or NOTUBE respectively may be
used.
To allow you to add an external co-processor, sometimes referred to as
a second processor, you may switch from using the internal TUBE to
the external TUBE. This is also carried out using the *CONFIGURE
command, this time with INTUBE and EXTUBE respectively.
For further information on the *CONFIGURE command see the REFERENCE
MANUA Part 1.
SYSTEM MEMORY
The following information explains the way in which the memory of
both the I/O processor and the co-processor are configured. It is
only intended as a general introduction to the memory usage of the
two processors. For a more full explanation of the way in which the
memory is configured please refer to the REFERENCE MANUA .
Please note that whilst a general understanding of the systems'
memory configuration may be of use, it is by no means essential.
Figure 2 shows the memory map for the I/O processor when it is
working with the 65C102 co-processor.
DISTINGUISHING BETWEEN MEMORIES
You will have noticed from the memory map that both the I/O processor
and the co-processor are numbered from &0000 to &FFFF. With the co-
processor working, the various filing systems must have a way of
distinguishing between the two memories in order to SAVE or OAD
programs into the correct place. This is done by defining the co-
processor memory as running from &0000 to &FFFF, and the I/O processor
memory from &FFFF0000 to &FFFFFFFF.
For example, memory location &C000 resides, by definition, in the co-
processor: memory location &FFFFC000 resides in the I/O processor.
Suppose you run a machine-code program which resides in the co-
processor from memory location &6000 to &6500. This program draws a
pretty picture on the screen in MODE 1, and you would like to save
both the program and the resulting picture onto disc.
To save the program onto disc, you would type:
*SAVE GRAFPRG 6000 6500 <RETURN>
where GRAFPRG is the filename you have chosen. To load and run the
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program from disc, you would type:
*RUN GRAFPRG <RETURN>
The program would be loaded back into the co-processor rather than
the I/O processor (no leading 'FFFFs' in the load address and end
address), and would run.
To save the resulting picture onto disc, you would have to save the
screen memory used in MODE 1, this resides in the I/O processor.
MODE 1 screen memory starts at &FFFF3000 and ends at &FFFF7FFF (ie
memory locations &3000 to &7FFF in the I/O processor). To save the
resulting picture, you would type:
*SAVE PICTURE FFFF3000+5000 <RETURN>
where PICTURE is the filename you have chosen. If you now reload
this by typing:
* OAD PICTURE <RETURN>
the file PICTURE will be loaded into the I/O processor, and as long as
you are already in MODE 1, the picture will reappear. (From this you
can probably deduce why some programs that directly access the screen
will not work with the co-processor.)
Note: It is not possible to save a shadow screen in this way. To save
or load a shadow screen you must make use of either the OSWORD calls
&5 and &6, or the *FX114 command to 'switch' SHADOW RAM into the main
memory map. For further information, please refer to the REFERENCE
GUIDE.
You may have noticed that when you execute a *INFO on a disc file,
addresses are preceded by either 00 or FF, rather than 0000 and FFFF.
For example typing:
*INFO PICTURE <RETURN>
might display
$.PICTURE FF3000 FF3000 FF4FFF 07A
and typing
*INFO GRAFPRG <RETURN>
might display
$.GRAFPRG 006000 006000 000500 05B
The disc filing system ignores the two most significant bytes of the
addressing, the cassette filing system displays the addressing in
full.
10

IMPORTANT: It is only the filing systems that recognise these '
extended' addresses. Current versions of BASIC an HI-BASIC make no
such distinction. Only the memory in the co-processor can be directly
accessed from BASIC. This means that using the ?,! and $ indirection
operators to access memory locations in the I/O processor from the
co-processor doesn't work, for example:
?&FFFF2000=&55 <RETURN>
will put the value &55 into memory location &2000 in the co-processor
and not into the location &2000 in the I/O processor as specified by
the leading FFFFs.
The same applies to saving and loading BASIC programs. If you save a
BASIC program to disc or cassette from the microcomputer, executing a
*INFO will display addresses with leading FFs. Saving a BASIC program
from the co-processor and executing a *INFO will display addresses
with leading 00s. However, BASIC will always load either program into
whichever processor is currently running BASIC.
It is possible to read and write to memory locations in the I/O
processor memory, this is done using OSWORD calls 5 and 6. OSWORD
calls are dealt with in the REFERENCE MANUA Part 1. A more advanced
description of TUBE communication techniques is contained within the
ADVANCED REFERENCE MANUA .
The 65C102 co-processor support disc
The disc supplied with the 65C102 contains 3 pieces of software,
these are:
HiBASIC
HiEDIT
Printer buffer utility
Hi languages
HiBASIC and HiEDIT are the same languages BASIC and EDIT that are
already resident in your machine. They only differ from the inherent
versions in the position that they expect to occupy within the memory
map.
If we consider the memory map of the microcomputer without a co-
processor attached (fig.2), we can see that BASIC normally resides
between &8000 and &BFFF. If BASIC were allowed to do this within the
co-processor, it would substantialy reduce the amount of RAM available
to the users programs. HiBASIC is supplied to overcome this
situation, it does so by locating itself between addresses &B800 and
&F7FF in the co-processor thereby allowing the user to maximise the
RAM available. HiEDIT, in this respect, acts in exactly the same way
as HiBASIC.
11

To use either HiBASIC or HiEDIT, insert the 65C102 support disc into
the disc drive and enter:
*HiBASIC <RETURN>
(or)
*HiEDIT <RETURN>
depending on the language you wish to use.
Printer buffer utility
On the 65C102 Support Disc, along with HiBASIC and HiEDIT, you will
find a file called BUFFER. •
A buffer is an area of RAM that is used as a 'holding area' for data
that is in transit between the microcomputer and an external device.
The RAM may be part of either the microcomputer, or the external
device, and is part of the communications pathway through which the
two devices communicate.
The size of a particular buffer can make a considerable difference to
the speed and efficiency of a given data transfer. In the case of the
microcomputers' printer buffer, there is a 256 byte area of RAM
allocated to this purpose. This means that as soon as the
microcomputer has transmitted 256 bytes of data more than the printer
has accepted, the buffer will become full, and the microcomputer will
be forced to wait until more space becomes available in the printer
buffer.
The length of time the computer, and therefore the operator, spends
waiting is dependant upon three things:
a) The speed at which the printer can print
b) The size of the recieve buffer contained within the printer
c) The size of the transmit buffer in the microcomputer
Both a) and b) are determined by the design of the printer and are
not easily changed; the size of the default printer buffer in the
microcomputer is also fixed. It is however possible to re—allocate
the area of the microcomputers' memory to be used as a printer
buffer; this is the function of the printer buffer utility.
This utility provides you with an approximately 24 Kbyte buffer in
the I/O processor for use with your currently selected printer. This
dramatic increase in buffer size means that the computer will not
have to wait for the printer unless the data to be printed exceeds 24
Kbytes. In the instance of a text file, this may be considered to be
roughly equivalent to 24 A4 pages of text, sufficient to hold the
entire textual content of this manual with room to spare!
12

This buffer uses RAM in the I/O processor between &4000 and &8000
and should not be used where your own application makes use of this
area of I/O memory. Since the area of memory used by the printer
buffer utility is the same as that available to the user when a co-
processor is not in use; this utility may only be used in
conjunction with a co-processor.
To make use of the printer buffer utility, you should enter:
*BUFFER
It is important to realise that, whilst you are able to continue
using a word processor, or other language resident in the co-
processor, it is not possible to make use of the main RAM in the I/O
processor whilst the printer buffer is in use. This will preclude
the use of a number of other utilities such as AFORM and the Q
parameter available with the sideways RAM utilities. Also, you
should realise that a 20 Kbyte text file can take as much as 15
minutes to print on a slower printer. The microcomputer should be
neither reset or switched off whilst the printer is still printing.
For further information on the use of printers, please refer to the
WE COME GUIDE that accompanied the microcomputer.
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