AS-Interface Slave IC

AS2701A (ISA3+)

Rev. C, October 2000

Page 4 of 16

Functional Descriptio n

The IC identifies and decodes the supply voltage overlapping signals of the master telegram. If

the slave address contained within the master telegram coincides with the stored information

in the E

AS-Interface slave IC is executed.

After decoding of the master telegram the addressed AS-Interface slave IC responds with a

corresponding slave answer on the AS-Interface line.

The AS-Interface slave IC extracts its own supply voltage and the supply voltage for the

E

peripheral UOUT which results from U

The receive block detects the signal on the AS-Interface wire LTGP. The reference voltages of

the signal comparators are (52.5 ± 5) % of the maximum signal value and are controlled by a

peak value detector in the following mode: The comparator level is set to its default value by

Reset or if a non-correct signal is received.

If a line pause is detected, the level reset is released and the IC is able to adapt itself to

different signal levels. If the IC is not synchronized yet, the level adaption is faster (smaller

attack and decay time constants) as in the synchronous case.

The output information of the receive blocks are the signals: "imp_pos" and "imp_neg".

The transmit block drives the output level for the modulated transmit signal edges. The

transmit block consists of the NMOS transistor (transmit transistor), DAC for transmit signal

formation and a Jabber-Inhibit Circuitry. The DAC is addressed by the digital block. If the

transmitter is active more than typ. 300µs the Jabber-Inhibit circuit separates the IC from the

AS-Interface line. This condition can only be left by a Power-On-Reset.

In the digital block the received signal is analyzed, the transmit signal is generated and the

data and parameter ports as well as the E

acts as a serial two-wire interface with the following transmission streams:

After the AS-Interface slave IC has sent the START condition, the device address is

transmitted. This address would allow the selection of a maximum of 8 possible E

is however fixed to 000 by the AS-Interface slave IC. Therefore in the application pins AO...A2

of the E

Device-Address

1

1

0

0

A2

A1

A0

1

Data

P

S

SDA

S

1

1

0

0

A2

A1

A0

0

Device-Address

Byte-Address

Byte Read Cycle

SDA

S

1

1

0

0

A2

A1

A0

0

Device-Address

Byte-Address

Byte Write Cycle

Data

P