JAJSQ97 データシート

JAJSQ97J may 2009 – january 2021 XIO2001

PRODUCTION DATA

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）

PNP|128
- MPQF060E
ZWS|169
- MPBGAK4B
ZAJ|144
- MPBG878A

サーマルパッド・メカニカル・データ

PNP|128
- PPTD154D

発注情報

8.3.7 PCI Express to PCI Bus Lock Conversion

The bus-locking protocol defined in the PCI Express Base Specification and PCI Local Bus Specification is provided on the bridge as an additional compatibility feature. The PCI bus LOCK signal is a dedicated output that is enabled by setting bit 12 in the general control register at offset D4h. See Section 8.4.66, for details.

Note:

The use of LOCK is only supported by PCI-Express to PCI Bridges in the downstream direction (away from the root complex).

PCI Express locked-memory read request transactions are treated the same as PCI Express memory read transactions except that the bridge returns a completion for a locked-memory read. Also, the bridge uses the PCI LOCK protocol when initiating the memory read transaction on the PCI bus.

When a PCI Express locked-memory read request transaction is received and the bridge is not already locked, the bridge arbitrates for use of the LOCK terminal by asserting REQ. If the bridge receives GNT and the LOCK terminal is high, then the bridge drives the LOCK terminal low after the address phase of the first locked-memory read transaction to take ownership of LOCK. The bridge continues to assert LOCK except during the address phase of locked transactions. If the bridge receives GNT and the LOCK terminal is low, then the bridge deasserts its REQ and waits until LOCK is high and the bus is idle before re-arbitrating for the use of LOCK.

Figure 8-6 Starting a Locked Sequence

Once the bridge has ownership of LOCK, the bridge initiates the lock read as a memory read transaction on the PCI bus. When the target of the locked-memory read returns data, the bridge is considered locked and all transactions not associated with the locked sequence are blocked by the bridge.

Figure 8-7 Continuing a Locked Sequence

Because PCI Express does not have a unique locked-memory write request packet, all PCI Express memory write requests that are received while the bridge is locked are considered part of the locked sequence and are transmitted to PCI as locked-memory write transactions.

The bridge terminates the locked sequence when an unlock message is received from PCI Express and all previous locked transactions have been completed.

Figure 8-8 Terminating a Locked Sequence

In the erroneous case that a normal downstream memory read request is received during a locked sequence, the bridge responds with an unsupported request completion status. Note that this condition must never occur, because the PCI Express Specification requires the root complex to block normal memory read requests at the source. All locked sequences that end successfully or with an error condition must be immediately followed by an unlock message. This unlock message is required to return the bridge to a known unlocked state.