AM 320-01-808
20
3. SL 5 (Slave)
Each slave produces up to four freely programmable,
complex sounds with two sound components each. The
sounds can be assigned to the upper manual, lower manual,
accompaniment unit, MIDI or pedalboard as desired.
Also, several voices can be combined for one instrument.
Since each sound consists of two Waves, eight "audio
channels" are necessary for the four voices (IC 10-IC 17 =
DAC0832, IC 1-IC 4 = TL084).
As soon as a manual or pedalboard key is depressed, the
master loads the "2-Port-RAM" (IC 9, 6264) with the sound
parameters via the master bus. For internal processing
purposes, the "bus switch" switches the RAM over to the
slave bus: with IC 25, 26, 32, 33 (HC 157) the addresses
and control signals coming from slave and master are fed
through to the RAM, depending on the bus that is given
access to the RAM. Via the data bus driver IC 21 (HC1245
for slave bus) and IC 22 (HC245 for master bus), master
and slave can read the RAM or write on it.
To guarantee optima! data transfer, the cycle times 2MHz)
between master and slave processor (ME, MO to master,
SE, SO tor slave) are shifted by one half cycle. Thus, also
large data packages, for instance for complex voices, can
be read in and out with a quasi 4MHz cycle time because
the bus switch is constantly switching over from master to
slave bus and vice versa, so that both processors have
permanent access to the
RAM.
After loading the RAM (by the master), the slave CPU
starts and works off the internal program. By programming
the timer (IC 23, 9513), the readout rate is determined.
Four timers determine the pitch (read-out rate of the sound
parameter lists) and the fifth timer determines the' repeat
frequency for computing the envelope curve.
Via the sequence logic (IC 27 = HCT279, IC 20 = HCT-
574), the DMA controller (IC 31, 9517) and the eight Wave
DACs are controlled, which guarantees output of the sound
lists from the RAM without influence by the CPU. The
digital values for four voices with two components each are
loaded into the eight signal DACs (Write) and converted
into analog signal, if permission is given (data transfer =
XFER). Due to the fact that the interim storage and the
read-out process of the digital information are controlled
directly by the timer, correct and undistorted analog signals
are produced, independent of internal work cycles.
At the same time, the envelope DAC (IC 18, DAC1232)
converts its digital information for eight voice components.
Via the 8-channel de-multiplexer (IC 6, 4051) and the
Sample&HoId stages (IC 1-IC 4a, d, TL084), the eight
envelope voltages are distributed among the eight signal
DACs, which act as multiplying DACs and directly
determine the volume levels of the respective analog
signals.
The crosspoint matrix (IC 7, 8, MC145100) causes the
audio signals to be fed through to one of the five slave
channels.
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