Common Dma Problems; D/A Conversions (Ada1200 Only) - Real Time Devices AD1200 User Manual

. Common DMA Problems
. Make sure that your buffer is large enough to hold all of the data you program the DMA controller to transfer.
. Check to be sure that your buffer does not straddle a page boundary.
. Remember that the number of bytes for the DMA controller to transfer is equal to twice the number of
samples. This is because each sample is two bytes in size.
' If you terminate sampling before the DMA controller has ransferred the number of bytes it was programmed
for, be sure to disable DMA by setting the mask bit in the single mask register.
. lvlake sure tlat the board is not running too fast for DMA transfers.
D/A Conversions (ADA1200 Only)
The two D/A converters can be individually programmed to convert 12-bit digital words into a voltage in the
range of +5, +10, 0 !o +5, or 0 to +10 volts. DACI is programmed by writing the 12-bit digital data word to BA + 8.
DACZ is identical, with the daa word'written to BA + 10. The foltowing tables list the key digital codes and
corresponding output voltages for the D/A converters.
D/A Converter Unlpolar Callbration Table
D/A Blr Welghr
ldeal Output Voltage (in mllllvolts)
0 t o + 5 V 0 t o + 1 0 V
4095 (Max. Output)
4998.8 9997.6
2048
2500.0 5000.0
1024
1250.0
2500.0
512
62s.00
1250.0
256
312.s0
62s.00
128
1s6.250 312.s0
64
78.125 156.250
s2
39.063 78.12s
1 6
1 9 . 5 3 1 3 39.063
8
9.76s6
19.5313
4
4.8828 9.76s6
2
2.4414
4.8828
1 1.2207
2.4414
0
0.0000
0.0000
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