Tait TM8000 Series, Руководство по применению

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54 Programmable I/O Lines TM8000 3DK Hardware Developer’s Kit Application Manual
September 2003 © Tait Electronics Ltd
3.1.12 BCD Pin 0 to 4
Application
These signals are used to select a discrete channel using a bit pattern on up
to five input lines.
BCD/BIN Operation
The bit pattern can be decoded in BCD or binary (BIN) operation.
In BCD operation, the bit pattern is divided into a block of four signals (pin
0 to 3) to provide the decimal numbers 0 to 9 (0000 to 1001), and a most
significant bit (pin 4) to indicate 0 or 1. This allows five lines to represent
the decimal channel numbers 1 to 19. Invalid BCD bit patterns are ignored.
In BIN operation, the bit pattern represents the decimal channel numbers
1 to 31.
When channel 0 is selected in either BCD or BIN mode, no channel change
occurs.
Table 3.3 shows a list of BCD pin signals and their equivalent BCD and BIN
channel numbers.
When any of these input lines changes, the corresponding channel will be
selected.
Table 3.3 BCD pin signals and BCD/binary channels
BCD Pin Channel
4 3 2 1 0 BCD BIN
0 0 0 0 0 No change
0 0 0 0 1 1 1
0 0 0 1 0 2 2
… … … … … … …
0 1 0 0 1 9 9
0 1 0 1 0 Prev
a
a. ‘Prev’ means that the input is ignored (invalid BCD) and that the previ-
ously selected channel remains selected.
10
0 1 0 1 1 Prev
a
11
… … … … … … …
0 1 1 1 1 Prev
a
15
1 0 0 0 0 10 16
1 0 0 0 1 11 17
… … … … … … …
1 1 0 0 1 19 25
1 1 0 1 0 Prev
a
26
… … … … … … …
1 1 1 1 1 Prev
a
31