DS2407 datasheet(16/31 Pages) DALLAS

16 / 31 page

DS2407

012099 16/31

available, bit 6 of the Channel Info Byte reads 1. For

1–channel versions of the DS2407, the PIO B sensed

level, channel flip–flop value, and activity latch value

should be ignored. Without an external supply, the sup-

ply indication bit (bit 7) reads 0. As long as the voltage

applied to the VCC pin is high enough to operate the

device this bit will read 1.

CHANNEL CONTROL BYTE 1 Figure 7a

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

Activity

latch reset

TOG

CHS1

CHS0

CRC1

CRC0

CHANNEL CONTROL BYTE 2 Figure 7b

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

THE EFFECT OF TOGGLE MODE AND INITIAL MODE Figure 7c

TOG

CHANNELS

EFFECT

one channel

Write all bits to the selected channel.

one channel

Read all bits from the selected channel.

one channel

Write eight bits, read eight bits, write, read, etc. to/

from the selected channel.

one channel

Read eight bits, write eight bits, read, write, etc.

from/to the selected channel.

two channels

Repeat: four times (write A, write b)

two channels

Repeat: four times (read A, read B)

two channels

Four times: (write A, write B), four times: (read A,

read B), write, read, etc.

two channels

Four times: (read A, read B), four times: (write A,

write B), read, write, etc.

CHANNEL INFO BYTE Figure 8

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

Supply

Indication

0=no sup-

ply

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

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