SBPH400-3 datasheet(21/43 Pages) STMICROELECTRONICS

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SBPH400-3

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2.8.7 Status transfer

A 4-bit status transfer of S[0:3] is initiated by the SBPH400 when any of the four status bits

S[0] to S[3] (as specified in Table 2.13) is set to 1. A 16-bit status transfer of s[0] to s[15] (as

specified in Table 2.13 is initiated by the link in response to a register read request from the

link device, or to indicate the node’s new phy_ID after a bus reset during the Self_ID process.

After the link interface is idle, a status transfer is initiated with the assertion of status (CTL[0:1]

= 10) condition by the SBPH400. The first two bits of status information (S[0:1]) are made

available on D[0:1]. The status condition is held on CTL[0:1] for the duration of transfer. The

SBPH400 ensures that there is at least one clock cycle between status transfers.

Figure 2.11

Status transfer timing

Table 2.13

Status bits

Bit (S[n])

Name

Description

ArbitrationResetGap

This bit indicates that the SBPH400 has detected that the

serial bus has been idle for an arbitration reset gap time (this

is defined in the IEEE 1394 standard). This bit is used by the

link device in the busy/retry state machine. This bit is reset

after the status transfer or when a transfer occurs on the bus.

SubactionGap

This bit indicates that the SBPH400 has detected that the

serial bus has been idle for a subaction gap time (this is

defined in the IEEE 1394 standard). This bit is used by the link

device to detect the end of an isochronous cycle. This bit is

reset after a status transfer or when a transfer occurs on the

bus.

BusReset

This bit indicates that the SBPH400 has entered the bus reset

state. This bit is reset after a status transfer

PHY_Interrupt

This bit is set whenever any of the interrupt-generating status

bits (Loop detect, Power fail, State time-out, Port event) is set

to 1. This bit is reset after a status transfer.

4-7

Address

These bits indicate the address of the SBPH400 register

whose contents are being transferred to the link device

8-15

Data

These bits provide the current value of SBPH400’s register.

S[0,1]

S[2,3]

S[14,15]

SBPH400

CTL[0:1]

SBPH400

D[0:1]

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