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Master 128 CMOS

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Master Battery Backup Fitting Instructions And CMOS RAM Hints.

What To do When it All Goes to Pot.

Updated 10/12/1999

Some Masters have a shrink wrapped pack of batteries. Some have a battery holder. If yours has a battery holder, then you can replace the 3 AA sized batteries. Place some tape around the whole unit to ensure the batteries are secure in the holder.

Ensure that your Master is not plugged into the mains!

Remove the cover of your Master by undoing the 4 screws underneath the case marked 'FIX'.

Locate the old battery pack. Usually, the shrink wrapped type are pushed down the side of the keyboard. The battery holder type are taped to a plate, the plate is screwed onto the case between the power supply (the large metal box to the left of the main circuit board) and the circuit board. If you are replacing a battery holder type, then re-use the plate and screws if there is no corrosion. If you are not re-using a plate and screws, use a self adhesive velcro strip or double sided sticky pad.

Remove the plug from the socket, do not pull the wires, grip the socket housing and gently pull it upwards. Remove the old battery pack from your Master. Dispose of the old unit, please do not throw expired batteries in the bin, they should be placed in the special containers you can find at public tips.

Place the new unit into the space between the power supply and the main circuit board, slide it so it comes slightly under the keyboard, resting it over the slots in the casing.

Push the plug onto the three pins on the main circuit board. You should be able to fit the plug on either way and the battery backup should work OK. If you encounter problems with the CMOS losing its settings after replacing the batteries, try turning the plug around.

Replace the cover and 4 screws.

The CMOS Settings. Hints.

The CMOS RAM holds all your default settings such as the mode and default filing system. When the batteries that maintain the CMOS RAM start to get low, usually the TIME$ function (Type *TIME) goes first. You will get a lot of gobbledegook instead of the date and time. This is a warning, you should swop the batteries as soon as possible.

Even with no battery backup, the CMOS RAM can retain its settings for a short while after the computer is turned off. This is a useful feature, if you replace the batteries before the problems (described below) appear, you should not need to enter all your CMOS settings again.

If you have the common problem of a locked up Master when you switch on, you will need to reset your Master and enter some CMOS settings to get you up and running. Incidentally, if you want to go through the following procedure each time you switch on, then you can manage without a battery back up at all!

Sorting out a Locked Up Master.

If you have re-fitted a battery pack to a Master and switch on to find that it is a right mess, do this:

Switch off.

Switch on whilst holding 'R' (RESET)

The computer comes up with the following:

CMOS RAM reset

Press break to continue

So do as it says and press BREAK.

Unfortunately, quite often, the computer now defaults to ADFS and tries to read in an ADFS catalogue from disc. If you have not got an ADFS disc in the drive, you will not be able to get any further. If this is the case:


Your Master should now say:

Acorn MOS

Acorn 1770 DFS

This is not a language *_

Type the following:


press RETURN



press RETURN, then press:


You are now in a position to use your computer. You can manually re-enter all the settings or use the PANEL program from the Welcome disc.

Master 128 CMOS Initial settings according to the Master Welcome Guide:


Setting the TIME function can be tricky as you have to get the syntax exactly right. Here is an example:

TIME$="Fri,10 Dec 1999.10:45:00"

There are two spaces in the string. The first space is between 10 and Dec, the second between Dec and 1999

Other Useful Tips.

Typing *CONFIGURE gives you an idea what settings there are. *STATUS tells you what most of your settings are at the moment. The Master Reference Manual Part 1 section C5-2 lists most of the possible settings and variations..

None of the changes you make with the *CONFIGURE command are recognised until you do a hard break or switch off. A hard break is when you press CTRL+BREAK (plus another optional key such as D, A or F). D if you want DFS, A if you want ADFS or F if you want FADFS. FADFS is ADFS but without reading in a catalogue from a disc.

I use a short program that inserts the CMOS settings for me. I have blown it onto EPROM (with a few other useful odds and ends). After going through the procedure described above, I then run the program which then sets all my preferred settings. All that needs setting then is the TIME$. Another way is to have your settings stored in a *EXEC file. You will have to refer to your manual to find out more.

Common problems with low batteries are:

TIME$ (type *TIME or PRINT TIME$) is corrupted.

Occasionally when you switch on, it doesn't come on in the mode or filing system you expected.

A ROM you have fitted stops working. This may be caused by the slot becoming UNPLUGGED (Type *ROMS, the word 'unplugged' appears next to the ROM title.) To cure this you can use *INSERT <ROM number>. Remember to do a hard break afterwards. Any of the ROMS could be affected, this includes BASIC which means that you may encounter the message 'This is not a language' when you switch on. Type *CONFIGURE LANG &C, press RETURN, then CTRL+D+BREAK to fix that one.

The auto repeat of your keyboard changes.

Your printer stops working because Printer Sink has come on (type *STATUS and after the word 'Print' is the number 0. It should be 1 for a Centronics type printer). Type *CONFIGURE PRINT 1.

Any of the settings could change at random. The answer is to change the batteries once a year.

The batteries are not used while your computer is switched on.

A charge is sent to the battery pack whilst the computer is on. There is a diode and resistor in the replacement pack that I make up, otherwise ordinary batteries may explode. I have discovered that the charge varies between different Masters from .5v to 4.5v. The top and bottom pins are negative, the center pin is positive.

It is worth considering using rechargeable batteries in the pack, in which case the diode could be removed. Bear in mind that the charge varies and NICAD batteries go flat suddenly.

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