BM2Timer

This little gem plugs into your 28-pin socket that normally takes a 27C256 chip.

This is used to put two tuning files of 32kb on a 64kb chip (XXX512 chip) and switch between one or the other tune file.

The BM2Timer V1.1 (and newer) has 2 methods for changing between tunes:

• Blue 2Pin Jumper (method which requires no additional equipment)
• External switch (method which requires a switch not included)

Blue 2Pin Jumper Method

With this Method you simply need to move the 2Pin blue jumper from pins 1-2 to pins 2-3 to switch between the two tunes.

• When the jumper is on the pins 1-2, it's for tune #2 (use 0000 to 7FFF chip region)
• When the jumper is on the pins 2-3, it's for tune #1 (use 8000 to FFFF chip region)

External Switch Method

It can has a single wire lead coming off of it using the middle pin (pin #2).

• When sorting this wire to ground you will run on the tune #2. If this wire is in open circuit (not connect to ground or any source), it will be on tune #1.

Clic HERE to Obtain the BM2Timer

Simple Connection 'Diagram' when using External Switch:

Middle pin (Pin#2) -> Wire -> Switch (one end)

Switch (other end) -> Ground

The switch must be a toggle switch (SPST or SPDT) if you want to switch from one tune to another without holding the button, otherwise if you want to change tune only when the button is held, use a momentary switch.

COMPATIBLE CHIPS

• 27C512
• W27C512
• W27E512
• 27SF512 SST
• XXX512

This is the requirement if the model you use aren't listed above:

Any 28pin Chips that end by (or has) the '512' marking on them, that are '64kb X8' and that the Pin #1 represent 'A15' will works.

If it has the 512 marking (its also a 64kb X8 chip) but the pin #1 doesn't represent A15 it'll not be a compatible chip!

ADDRESSING INFORMATIONS

• The first Tune are using chip addressing 8000-FFFF
• The second Tune are using chip addressing 0000-7FFF

HOW TO BURN A CHIP FOR THE BM2Timer

With the software that goes with your eprom programmer (chip burner), you will start by selecting your chip model.

1. Erase the chip (if it is blank avoid this step)
2. Open your Tune #2 file (yes #2)
3. Burn this file from 0000 to 7FFF
4. Then open your Tune #1
5. Burn this file from 8000 to FFFF
6. Now your chip is ready to be used, it includes your two files!

Parts List to build your BM2Timer PCB

• 1x 10K Ohms 1/6w Resistor(Can be almost any value actually, doesn't need to be perfectly 10K Ohms)
• 1x 2Pins Jumper
• 1x Female Jumper Wire(Only if you use Extrenal Button switch)
• 1x 3Pins Male Angle Header**
• 2x 14Pins Male to Male Round pin header**
• 2x 14Pins Male to Female Header** OR 1x 28Pins DIP Socket

**These parts usually come in 40Pins rows that you have to cut to the desired lenght

BM2Timer V1.1

Circuit Schematic Diagram