ADPRO VM22A, Issue 6
21
8.0 Serial
Protocol
In VM22A mode, channel selection is achieved using a serial protocol via the BCD
signal lines. Figure 10 shows the serial protocol timing diagram, and Table 4 shows
the relationship of the serial signals to the BCD lines.
SERIAL PROTOCOL
Expansion I/O Pin
Signal Line
Function
14
BCD 0
Serial Clock
7
BCD 1
Serial Data
15
BCD 2
Serial Strobe
Table 4 – Relationship of the Serial Signals to the BCD lines
Figure 10 – Serial Protocol Timing diagram
A3
A2
A1
A0
D3
D2
D1
D0
Clock
Data
Strobe
>0 seconds
>0 seconds
15nS data settle
t 0
A ..A is the Unit ID in binary format (A is LSB).
D ..D is the channel in inverse BCD format, refer to
Table 3 (D is LSB).
0
3
0
0
3
0
Where:
