Rainbow Electronics DS2406 - Manual (Page 16)

DS2406
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After the Channel Control bytes have been transmitted the bus master receives the Channel Info byte
(Figure 9). This byte indicates the status of the channel flip-flops, the PIO pins, the activity latches as
well as the availability of channel B and external power supply. To be able to read from a PIO channel,
the output transistor needs to be non-conducting, which is equivalent to a 1 for the channel flip-flop.
Reading 0 for both the channel flip-flop and the sensed level indicates that the output transistor of the PIO
is pulling the node low. For the Channel Info byte PIO A and B are sampled at the same time, as in the
synchronous mode. If channel B is available, bit 6 of the Channel Info Byte reads 1. For 1-channel
versions of the DS2406, the PIO B sensed level, channel flip-flop value, and activity latch value should
be ignored. Without an external supply, the supply indication bit (bit 7) reads 0. As long as the voltage
applied to the V
CC
pin is high enough to operate the device this bit will read 1.
CHANNEL INFO BYTE Figure 9
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
Supply
Indication
0 = no
supply
Number of
Channels
0 = channel
A only
PIO-B
Activity
Latch
PIO-A
Activity
Latch
PIO B
Sensed
Level
PIO A
Sensed
Level
PIO-B
Channel
Flip-Flop Q
PIO-A
Channel
Flip-Flop Q
ONE-CHANNEL READ/WRITE Figure 10a
PIO
1-WIRE
READ (IC=0, Asynchronous Mode)
WRITE (IC=0, Asynchronous Mode)
PIO
1-WIRE
td1 td0 15 µs < td1 < 60 µs 200 ns < td0 < 300 ns
PIO SAMPLING
TWO-CHANNEL READ Figure 10b
PIO-A
PIO SAMPLING
1-WIRE
1-WIRE
PIO-B
IC=1, SYNCHRONOUS MODE
IC=0, ASYNCHRONOUS MODE
1 3 5 7 9 8 6 4 2
A1 B1 A3 B3 A5 B5 A7 B7 A9
A1 B2 A3 B4 A5 B6 A7 B8 A9