DMM-16R-AT User Manual V1.31
www.diamondsystems.com
Page 14
6.
REGISTER DEFINITIONS
Base + 0
Read
A/D LSB
Bit No.
7
6
5
4
3
2
1
0
Name
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
Definitions:
AD7
– 0
A/D data bits 7 - 0; AD0 is the LSB; A/D data is a signed 16-bit value ranging from -32768 to
+32767.
Base + 0
Write
Start A/D Conversion
Writing to Base + 0 starts an A/D conversion. The value written does not matter.
Base + 1
Read
A/D MSB
Bit No.
7
6
5
4
3
2
1
0
Name
AD15
AD14
AD13
AD12
AD11
AD10
AD9
AD8
Definitions:
AD15
– 8 A/D data bits 15-8; AD15 is the MSB
Note: Reading from Base + 0 and Base + 1 result in the same physical operation, reading from the
FIFO.
The FIFO is 8 bits wide, with A/D data stored and retrieved in interleaved fashion. Data from the A/D is put
into the FIFO in little-endian mode, with the LSB inserted first, and the MSB inserted second. Thus the data
comes out of the FIFO in the same order. Each time a byte is read from either Base + 0 or Base + 1, the next
byte will be read from the FIFO and the FIFO counter will be decremented.
Because the FIFO decrements after each read operation, you cannot read the same value more than once
(unless the FIFO is empty, in which case the last byte may be read indefinitely). It is the programmer’s
responsibility to ensure that data is read out of the FIFO properly so that appropriate pairs of bytes are read
out together.
Base + 1
Write
D/A LSB
Bit No.
7
6
5
4
3
2
1
0
Name
DA7
DA6
DA5
DA4
DA3
DA2
DA1
DA0
Definitions:
DA7-0
D/A bits 7-0; DA0 is the LSB. D/A data is an unsigned 12-bit number ranging from 0 to 4095.