Kurzweil K250 - Page 57

· ·l The CPU is then interrupted (level 6) and must read the
)
contents of the vector to determine which channel and which span to
update. This also clears the interrupt. During the time between the
interrupt and the reading of the vector, End-of-Waveform
in
Progress (EOWIP) is set.
If there is an interrupt pending, the current CSW is modified to
have its End-of-Waveform Pending (EOWPEND) bit set. This is
examined every time the
CSW is read, and if active, the EOWIP signal
is sampled to determine whether the current EOWPEND can be made
active
("peeled") or remain pending. The vector and EOWPEND bit are
adjusted
accordingly.
How to operate a channel
1. Set up sampling and alias clock rates
write to 8254
control location
write 2 bytes to each clock location
2. Set up parameter block in CGP local memory
write
channel status word 0 x FFFF
write
DMA starting location (AM, AL)
write DMA high order address, interrupt vector
write
DMA last address
3. Write to approp~iate amplitude DAC
4. Enable channel via channel control location
To disable a Channel
1. Make sure AMP DAC is at minimum amplitude
2. Disable channel via channel control location
Kurzwell 250 Service Manual. Chapter 3
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