User manual

from the new memory bank. Switching will not change the note currently being played, but

affects all subsequent notes.

Here is a concrete example for the TB-303. The memory switches are set to:

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Bank 18

The Internal Sequencer is started and is playing Pattern 5B in Pattern Group III. Let's call

this "Pattern III-5B". The Internal Sequencer plays this pattern several times and then in the

middle of the pattern, while note 4 is playing, either the fifth toggleswitch ("4" in the above

chart) is lowered, or the pushbutton is pressed. Either action has the same effect of making

the fifth switch function (address bit 4) as a "low". So the bank select address bits are now

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Bank 2

As the CPU prepares to play the fifth note, it reads from memory, but instead of reading

Note 5 of Bank 18's Pattern III-5B, it reads Note 5 of Bank 2's Pattern III-5B. So the pitch,

Accent and Slide will vary as the banks are switched, but the CPU will take no notice of the

lengths and pre-scales of Bank 2's Pattern III-5B.

Switching banks whilst in Pattern Write, Track Write or Track Play modes will surely lead

to confusion of both the Internal Sequencer firmware and the user!

3 - Use in Track Play Mode

(This section does not mention Dynamic Bank/Channel Switching, which is an elaboration

upon the basic 32 Bank Memory system described here.)

When I first began modifying TB-303s, TR-606s and TR-808s in 1981/82 , it was to install

multiple memory banks. The purpose was to store more patterns and tracks so the users

could use the machines to accompany them on guitar, vocals, keyboards etc. Some of these

musicians had repertoires of hundreds of songs. In those systems I used pushbutton

switches, counters LEDs and/or 7 segment figure-8 LED displays to control and display the

current bank number. These memory systems were designed to reset the CPU whenever the

bank was changed. Therefore changing from bank 23 to bank 13 was like turning off one

drum-machine or TB-303 and turning on another. This was necessary, since there were

certain items of data in the Track memory which was only read when the CPU ran its

initialisation routines after being reset. (In the case of the TR-808, I made this reset circuit

disableable to allow for live switching between banks in Pattern Play mode.)

Without this automatic reset circuit, there was a grave danger of the user changing banks

whilst the CPU was running, and so causing it to become confused – particularly in regard to

the starting and ending points of tracks and the prescales and lengths of patterns.

Now that the primary use of the TB-303 / Devil Fish (and the TR-606 and TR-808) is real-

time manipulation rather than playing songs reliably, I have changed the memory control

system. The new system has no automatic reset circuitry at all.

This toggleswitch and pushbutton arrangement is simple, flexible and reliable. However, if

you are using Track Play mode and you switch banks whilst the machine is turned on, then it

is quite likely that the CPU's firmware will generate unexpected and undesirable results.