DS2406

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

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

13

5

7

8

6

4

2

A1

B1

A3

B3

A5

B5

A7

B7

A9

A1

B2

A3

B4

A5

B6

A7

B8

A9

9

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