AMSTRAD cpc 6128 User Instruction page 410
Integrated computer/disc system
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Also See for cpc 6128:
- Service manual (32 pages) ,
- Service manual (31 pages) ,
- Service manual (31 pages)
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Unless you are a very slow typist, you will have noticed that you were able to type in
the second of these commands before the first had finished. This is because the sound
system is able to hold up to 5 sound commands for each channel in a 'queue'. If we
wanted a sound to play on channel A, and then two,sounds to play simultaneously on
A and B, we would need some way ofletting the computer know that the sound on B
should not start until the second note on A was ready to play - i.e. making one channel
wait for another. This is known as a rendezvous, and there are two ways in which this
can be achieved:
SOUND 1,200,1000
SOUND 3,90,200
In this, the second note is directed to A and B, so it cannot start until the note on A
finishes. The limitation with using this method (to make a note combination wait
until all channels that it should play on are free) is that the same sound will be
directed to each of the channels (in this case, 90,200 went to both A and B). The
alternative method is to use the following:
SOUND 1,200,2000
SOUND 1+16,90,200
SOUND 2+8,140,400
Here, the second note on A is made to rendezvous with the sound on B (and the sound
on B is made to rendezvous with the note on A). The advantage here is clear
- although the second note on A was different to the note on B, the two were still
linked so that neither could start until both channels were free - this is a rendezvous.
Once again the values are bit-significant:
8
=
2
t
3,16
=
2
t
4, and 32
=
2
t
5
.... so now the channel number can be seen as a binary number where the columns are
headed:
Rendezvous
C
Add 32
Rendezvous
B
Add 16
Rendezvous
A
Add8
Play on
C
Add 4
Play on
B
Add 2
Play on
A
Add 1
So for a note to play on C and rendezvous with A, you would use:
o
o
1
1
o
o
This is the binary number 1100, which is equal to 8
+
4
=
12
Hence, a channel number of 12 would tell the computer to play a note on channel C,
and wait for a note that has been marked to rendezvous with it on channel
A.
At
your
leisure ....
Chapter 9 Page 37
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