TSB41AB2PAPG4 datasheet(34/55 Pages) TI1

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TSB41AB2, TSB41AB2I

IEEE 1394a2000 TWOPORT CABLE

TRANSCEIVER/ARBITER

SLLS424G − JUNE 2000 − REVISED DECEMBER 2004

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

LLC service request (continued)

Regardless of the type of request, a start bit of 1 is required at the beginning of the stream, and a stop bit of 0

is required at the end of the stream. The second through fourth bits of the request stream indicate the type of

the request. In the descriptions below, bit 0 is the most significant and is transmitted first in the request bit stream.

The LREQ terminal is normally low.

Encoding for the request type is shown in Table 13.

Table 13. Request Type Encoding

LR1 – LR3

NAME

DESCRIPTION

000

ImmReq

Immediate bus request. Upon detection of idle, the PHY takes control of the bus immediately without arbitration.

001

IsoReq

Isochronous bus request. Upon detection of idle, the PHY arbitrates for the bus without waiting for a subaction gap.

010

PriReq

Priority bus request. The PHY arbitrates for the bus after a subaction gap, ignores the fair protocol.

011

FairReq

Fair bus request. The PHY arbitrates for the bus after a subaction gap, follows the fair protocol.

100

RdReg

The PHY returns the specified register contents through a status transfer.

101

WrReg

Write to the specified register.

110

AccelCtl

Enable or disable asynchronous arbitration acceleration.

111

Reserved

Reserved.

For a bus request the length of the LREQ bit stream is 7 or 8 bits as shown in Table 14.

Table 14. Bus Request

BIT(S)

NAME

DESCRIPTION

Start bit

Indicates the beginning of the transfer (always 1).

1−3

Request type

Indicates the type of bus request. See Table 13.

4−6

Request speed

Indicates the speed at which the PHY sends the data for this request. See Table 15 for the encoding of this field.

Stop bit

Indicates the end of the transfer (always 0). If bit 6 is 0, this bit may be omitted.

The 3-bit request speed field used in bus requests is shown in Table 15.

Table 15. Bus Request

LR4 – LR6

DATA RATE

000

S100

010

S200

100

S400

All Others

Invalid

NOTE: The TSB41AB2 does accept a bus request with

an invalid speed code and process the bus

request normally. However, during packet

transmission for such a request, the TSB41AB2

ignores any data presented by the LLC and

transmits a null packet.

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