Roland MC-303 Groovebox User Manual download pdf (Page 6)

®ÂØÒÅˆÎ MC-303 Supplemental Notes

When computing the checksum, the sum of the address and data bytes may be greater than 80H. In this case the result

will be a negative checksum. When this happens, subtract 80H from the address and data sum as often as necessary

until the sum is less than 80H, so that the subtraction that computes the checksum yields a positive result. For instance:

80H - (80H + 40H + 01H + 40H + 06H) = Checksum

80H - 107H = Checksum (negative, so subtract 80H)

80H - (107H – 80H=87H) = Checksum (still negative, so subtract 80H again)

80H - (87H – 80H=07H) = Checksum (positive)

79H = Checksum

If you’re new to hex, you may be confused to see an equation like 80H – 07H = 79H. You may find it easier to

convert all the values to decimal, perform the subtraction, and then convert back. In this case, 128 (=80H) minus

7 (=07H) equals 121 (=79H). If you have a PC, you can use the calculator that comes with Windows to perform

these calculations in hex or decimal. Also, you can use the conversion chart on page 113 of your Owner’s

Manual.

For the MC-303, there is a slight variation on this message format when we want to affect parameters for a single

part in Sound Module mode. Look at the Part Parameter addresses (Starting on pg. 108) in the Owner’s Manual.

You will notice that many addresses here have an “x” in the third address byte. In hex, the 16 Parts of the MC-303

are numbered starting with 8. For part 1, x=8, for part 2, x=A, etc. For part 10, x=9, after which part 11 is

numbered 2, and so on. For this example, let’s say we want to change part 1 from MIDI channel 1 to channel 16.

First, we use the same six byte header, followed by the appropriate address as shown in the Patch Parameter list.

Notice we have set x=8 (part 1) in our third byte of the address. The data byte is set to MIDI channel 16 (OFH).

F0H 41H 10H 00H 03H 12H

00H 40H 1

8*H 02H

07H

Header Address (* sets to part 1) Data

Our checksum for this message would be:

80H – (00H + 40H + 18H + 02H + 07H) = Checksum

80H – 61H = Checksum

1FH = Checksum

Yielding:

F0H 41H 10H 00H 03H 12H 00H 40H 18H 02H

07H 1FH

F7H

Header

Address Data Checksum

End

Here are a few more examples:

Use the following message to set part 12 to random panning:

F0H 41H 10H 00H 03H 12H 00H 40H 13H 1CH

00H 11H

F7H

Header

Address Data Checksum

End

Use the following message to set the LFO waveform to Square for part 8:

F0H 41H 10H 00H 03H 12H 00H 40H 10H 39H

03H 74H

F7H

Header

Address Data Checksum

End

Use the following message to set the Chorus Macro to Flanger:

F0H 41H 10H 00H 03H 12H 00H 40H 01H 38H

05H 02H

F7H

Header

Address Data Checksum

End

Give these examples a try. You can create a sequence that will automatically call up your sounds on all 16 MIDI

channels. You can edit sounds to fit into your performance needs. You can re-create all of the functions of the

front panel “Realtime Modify” section on the MC-303. You can even use system exclusive commands to make the

MC-303 do things it normally won’t do from the front panel! With a little practice you too can become an official

“Groove Box Master.”

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Roland MC-303 Groovebox User Manual Page 6

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