Author: Mark Usher

MASTER 'WRITE-PROTECT' MODULE

Please refer to the diagram when installing the module.
Installation.
1. Turn off the computer.
2. Remove the top cover by undoing the four screws as explained on the underside of the computer.
3. Locate links 18 and 19, these are marked LK18 and LK19 on the computer board. These links are directly 'west' of ROM sockets 37 and 41 respectively, the ROM sockets being on the ’east' side of the computer and are probably empty. These links govern the use of ROM priorities, 4 and 5 – link 18, 6 and 7 – link 19. Their linking 'bridges' will be set to the EAST to access a ROM put into the appropriate socket; or to the WEST in order to use the computer's sideways RAM. The normal setting for both is WEST – i.e. for RAM. It is likely therefore, that at least one of these links will be set to the WEST, due to some sideways RAM being in use. Replace this WEST link with the module's two-wired connecter, the notch must face South, (see diagram). If both links were set 'WEST', then use the single-wired connector to replace the other 'bridge', with the single wire going to the centre of the three pins. If the second link was set to the EAST for ROM priority then the single-wire connector is not used.
4. If you are using all 4 sideways RAMs and wish to write-protect only 2 of these, then only connect the double-wired connector to the appropriate link, (see Stage 3 above), but don't forget that the linking 'bridge' must be in place on the other link, (in the WEST position for RAM, or the EAST position if you wish to insert a ROM).
5. Locate IC38. This is where the main module fits. The module must be pushed over IC38 with the black dot on the underside towards the notch on the chip, i.e. westwards. Make sure that all the legs of the module are in line with those of IC38 and not between the legs. The module should fit tightly over IC38, if it feels loose, gently bend the pins of the module inwards for a tighter grip. Note that pulling on the wires will probably dislodge the module, but this will not happen during normal use. The module uses a gold-plated header and there should be no problem with bad connections as long as it is installed correctly.
6. The module is now installed. The switch can either be trailed out through the back of the machine, or could be poked through one of the cartridge slots when putting the cover back on.
7. Replace the cover by reversing the procedure on the underside of the computer.

In use.
With write-protect 'on', the data held in sideways RAM cannot be altered, (unless you turn the computer off), although it can still be read. This can be used to prevent corruption of sideways RAM programs, and will enable you to transfer your 'awkward' ROMs to RAM, (i.e. those that write to themselves).
Don't forget to turn the write protect ’off' when loading programs into RAM'.
Note that if you are using BAS128 (which uses the sideways RAM for program storage), then you must turn the write-protect 'off’.
Hardware design copyright – APRIL, 1986 © VINE MICROS LIMITED. Designed by: R. P. D. Mallett.

VINE MICROS, MARSHBOROUGH, NR. SANDWICH, KENT, CT13 OPG. Tel. 0304 812276.