XIO2221 PCI Express™ 至 1394b OHCI（具有 1 端口 PHY）

The TI XIO2221 is a PCIe to PCI translation bridge, where the PCI bus interface is internally connected to a 1394b open host controller/link-layer controller with a 1-port 1394b PHY. The PCIe to PCI translation bridge is fully compatible with the PCI Express to PCI/PCI-X Bridge Specification, Revision 1.0. Also, the bridge supports the standard PCI-to-PCI bridge programming model. The 1394b OHCI controller function is fully compatible with IEEE Std 1394b and the latest 1394 Open Host Controller Interface (OHCI) Specification.

The XIO2221 simultaneously supports up to four posted write transactions, four nonposted transactions, and four completion transactions pending in each direction at any time. Each posted write data queue and completion data queue can store up to 8K bytes of data. The nonposted data queues can store up to 128 bytes of data.

The PCIe interface supports a ×1 link operating at full 250 Mbit/s packet throughput in each direction simultaneously. Also, the bridge supports the advanced error reporting capability including ECRC as defined in the PCI Express Base Specification, Revision 1.1. Supplemental firmware or software is required to fully utilize both of these features.

Robust pipeline architecture is implemented to minimize system latency. If parity errors are detected, packet poisoning is supported for both upstream and downstream operations.

PCIe power management (PM) features include active-state link PM, PME mechanisms, and all conventional PCI D states. If the active-state link PM is enabled, the link automatically saves power when idle using the L0s and L1 states. PM active-state NAK, PM PME, and PME-to-ACK messages are supported. The bridge is compliant with the latest PCI Bus Power Management Specification and provides several low-power modes, which enable the host power system to further reduce power consumption

Eight general-purpose inputs and outputs (GPIOs), configured through accesses to the PCIe configuration space, allow for further system control and customization.

Deep FIFOs are provided to buffer 1394 data and accommodate large host bus latencies. The device provides physical write posting and a highly tuned physical data path for SBP-2 performance. The device is capable of transferring data between the PCIe bus and the 1394 bus at 100M bit/s, 200M bit/s, 400M bit/s, and 800M bit/s. The device provides one 1394 port with cable bias (TPBIAS).

As required by the 1394 Open Host Controller Interface (OHCI) Specification, internal control registers are memory mapped and nonprefetchable. This configuration header is accessed through configuration cycles specified by PCIe, and it provides plug-and-play (PnP) compatibility.

The PHY provides the digital and analog transceiver functions needed to implement a 1-port node in a cable-based 1394 network. Each cable port incorporates two differential line transceivers. The transceivers include circuitry to monitor the line conditions as needed for determining connection status, for initialization and arbitration, and for packet reception and transmission. An optional external 2-wire serial EEPROM interface is provided to load the global unique ID for the 1394 fabric.

The XIO2221 requires an external 98.304-MHz crystal oscillator to generate a reference clock. The external clock drives an internal phase-locked loop (PLL), which generates the required reference signal. This reference signal provides the clock signals that control transmission of the outbound encoded information. The power-down (PD) function, when enabled by asserting the PD terminal high, stops operation of the PLL. Data bits to be transmitted through the cable ports are latched internally, combined serially, encoded, and transmitted at 98.304, 196.608, 393.216, 491.52, or 983.04 Mbit/s (referred to as S100, S200, S400, S400B, or S800 speed, respectively) as the outbound information stream.

To ensure that the XIO2221 conforms to IEEE Std 1394b-2002, the BMODE terminal must be asserted. The BMODE terminal does not select the cable-interface mode of operation. BMODE selects the internal PHY-section/LLC-section interface mode of operation and affects the arbitration modes on the cable. BMODE must be pulled high during normal operation.

Three package terminals are used as inputs to set the default value for three configuration status bits in the self-ID packet. They can be pulled high through a 1-kΩ resistor or hardwired low as a function of the equipment design. The PC0, PC1, and PC2 terminals indicate the default power class status for the node (the need for power from the cable or the ability to supply power to the cable). The contender bit in the PHY register set indicates that the node is a contender either for the isochronous resource manager (IRM) or for the bus manager (BM). On the XIO2221, this bit can only be set by a write to the PHY register set. If a node is to be a contender for IRM or BM, the node software must set this bit in the PHY register set.