AS-Interface Slave IC

AS2702 (SAP4.1)

Rev. C, January 2001

Page 15 of 18

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All slaves connected to an AS-interface bus are sequentially and cyclicly called by the master

in a string of individual transactions between the master and each slave unit.

A transaction consists of a 14 bits master request, typically containing the slave’s address as

well as data or parameter info, and an immediate acknowledging slave response of 7 bits.

The 14 bits master request - apart from Start Bit ST = 0 and End Bit EB = 1 – has the follow-

ing contents:

• 1 Control Bit CB: CB = 0 stands for data transfer (typ. data or parameters)

CB = 1 identifies command-type requests

• 5 Address Bits: A4, …, A0

• 5 Information Bits:

I4, …, I0 (typ. data or parameters)

• 1 Parity Bit PB.

AS2702 allows for up to 62 slaves on the same AS-interface bus; this requires a slave ad-

dress extended to 6 bits, hence an extra bit beyond A4, …, A0.

Information bit I3 is used as the 6

called Sel-bit, as it is perceived as to select between A-slave (Sel = 0) and B-slave (Sel = 1) at

address location A4, …, A0.

In non-extended address mode AS2702 is addressed with A4, …, A0 only - for a max. total of

31 slaves per AS-interface bus system, and is system compatible with existing slave device

AS2701A.

The 7 bits slave response – apart from Start Bit ST = 0 and End Bit EB = 1 – has the following

contents:

• 4 Information Bits:

I4, …, I0 (typ. data or parameters)

• 1 Parity Bit PB.

Detailed descriptions of all types of master requests and corresponding slave responses can

be found in AS-Interface Specification V2.11, obtainable from the AS-International Association

(D) or its local representative, see section “Application Support”.