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Page 18
Operation of the Card
Page 18
01270146.doc
Blue Chip Technology Ltd.
To operate in DMA mode updating a single channel use the following sequence:
Initialise the timer, as above.
Program timers 0 and 1 for the required output rate.
Write 0 to BASE + 1 and BASE + 2, this enables all the channels.
Program the DMA controller.
Write the channel number (1 to 12) + 240 to BASE + 0.
Start the DMA operation by reading BASE + 0.
Auto Channel Scanning
In DMA mode it is possible to output to all 12 channels by setting the AUTO
CHANNEL SCANNING bit in channel enable register 2.
When this bit is set, after each DMA transfer the channel number will be
incremented so the next DMA transfer will take place on the next channel.
When the channel reaches 12, it will continue to increment as if channels 13-16
were present, before resetting to channel 1.
To use this mode, the software must set-up a multi-dimensional array to store
the data for 16 channels (12 real + 4 phantom channels).
In BASIC:
DIM dataarray%(numsamples,16)
in C:
int dataarray[numsamples][16]
Software example 4 demonstrates the use of channel scanning.
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