Introduction

Thierry Peycru is working on speeding up the serial port. This can only be done on a real Z88 because OZvm the emulator does not emulate the Serial Port.

For this work he has to boot off the internal ROM and the Flash card located in slot 1. The constant inserting and removal of this card is creating problems with the connector making connection. Was it possible to have a switch, that either turned the Flash card on or off in slot 1 when doing a HARD RESET?

Back in the days when all software development was done on the Z88, the procedure for testing applications was a long and tedious process. The time it took to

• blow a 32K EPROM using an external EPROM program,
• trying it out on the Z88,
• 20 minutes to erase the EPROM again,

anything that could reduce that cycle would be welcomed.

The answer came in the form of a modified 32K RAM card.

Connecting a normally open reed switch on the read/write signal to the RAM, you could

• put the magnet near the card,
• write the code to the RAM,
• remove the magnet (which now made the RAM a 'Read only' device),
• test the application as if it was on a 32K EPROM card.

The same approach may be used here.

If a change over reed switch is used with the 1M 512K/512K Flash Card,

• cutting a track,
• using the existing decode chip
• and a pull up resistor,

the following option may be produced.

Modification to card

The Circuit

U4 is used to decode A19 to select either the top half of the memory for the flash chip or the bottom half of the memory map for the RAM. Only the Flash select line needs to be modified.

The normally closed part of the change over Reed switch is placed in the circuit on pin 5 (/CE1) to the Flash chip so that when the magnet is used, the chip select signal to the flash chip is broken. The pull up resistor on the normally open side of the reed switch will ensure that the Flash chip is NOT selected when in this state.

Extra components required