XIO2001IPNP datasheet(56/145 Pages) TI2

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8.4.30 Bridge Control Register

The bridge control register provides extensions to the command register that are specific to a bridge. See Table

8-27 for a complete description of the register contents.

PCI register offset:

3Eh

Read-only, Read/Write, Read/Clear

Default value:

0000h

BIT NUMBER

RESET STATE

Table 8-27. Bridge Control Register Description

BIT

FIELD NAME

ACCESS

DESCRIPTION

15:12

RSVD

Reserved. Returns 0h when read.

DTSERR

Discard timer SERR enable. Applies only in conventional PCI mode. This bit enables the

bridge to generate either an ERR_NONFATAL (by default) or ERR_FATAL transaction on

the primary interface when the secondary discard timer expires and a delayed transaction

is discarded from a queue in the bridge. The severity is selectable only if advanced error

reporting is supported.

0 = Do not generate ERR_NONFATAL or ERR_FATAL on the primary interface as a

result of the expiration of the secondary discard timer. Note that an error message

can still be sent if advanced error reporting is supported and bit 10

(DISCARD_TIMER_MASK) in the secondary uncorrectable error mask register

(offset 130h, see Section 8.5.10) is clear (default).

1 = Generate ERR_NONFATAL or ERR_FATAL on the primary interface if the

secondary discard timer expires and a delayed transaction is discarded from a

queue in the bridges.

DTSTATUS

RCU

Discard timer status. This bit indicates if a discard timer expires and a delayed transaction

is discarded.

0 = No discard timer error

1 = Discard timer error

SEC_DT

Selects the number of PCI clocks that the bridge waits for a master on the secondary

interface to repeat a delayed transaction request. The counter starts once the delayed

completion (the completion of the delayed transaction on the primary interface) has

reached the head of the downstream queue of the bridge (i.e., all ordering requirements

have been satisfied and the bridge is ready to complete the delayed transaction with the

initiating master on the secondary bus). If the master does not repeat the transaction

before the counter expires, then the bridge deletes the delayed transaction from its queue

and sets the discard timer status bit.

0 =

1 =

The secondary discard timer counts 215 PCI clock cycles (default)

The secondary discard timer counts 210 PCI clock cycles

PRI_DEC

Primary discard timer. This bit has no meaning in PCI Express and is hardwired to 0b.

FBB_EN

Fast back-to-back enable. This bit allows software to enable fast back-to-back transactions

on the secondary PCI interface.

0 = Fast back-to-back transactions are disabled (default)

1 = Secondary interface fast back-to-back transactions are enabled

SRST

Secondary bus reset. This bit is set when software wishes to reset all devices downstream

of the bridge. Setting this bit causes the PRST signal on the secondary interface to be

asserted.

0 = Secondary interface is not in reset state (default)

1 = Secondary interface is in the reset state

XIO2001

SCPS212J – MAY 2009 – REVISED JANUARY 2021

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