ADS7864
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SBAS141A–SEPTEMBER 2000–REVISED MARCH 2005
Table 2. Channel Truth Table
OUTPUT CODE (DB15…DB0)
DATA CHANNEL
DB14
DB13
DB12
The ADS7864 has a 16-bit output word. DB15 is ‘1’ if
the output contains valid data. This is important for
the FIFO mode. Valid Data can be read until DB15
switches to 0. DB14, DB13 and DB12 store channel
information as indicated in Table 2 (Channel Truth
Table). The 12-bit output data is stored from DB11
(MSB) to DB0 (LSB).
A0
A1
B0
B1
C0
C1
0
0
0
0
1
1
0
0
1
1
0
0
0
1
0
1
0
1
BYTE—If there is only an 8-bit bus available on a
board, then Byte can be set high (see Figure 29 and
Figure 30). In this case, the lower eight bits can be
read at the output pins DB7 to DB0 at the first RD
signal, and the higher bits after the second RD signal.
HOLDA
HOLDC
BUSY
CS
RD
BYTE
Figure 29. Reading Data in Cycling Mode
CS
RD
BYTE
A0
A0
A1
A1
B0
B0
B1
C0
C1
A0
LOW
HIGH
LOW
HIGH
LOW
HIGH
Figure 30. Reading Data in Cycling Mode
17
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