Intel 31244 PCI-X manual Serial ATA Interface, Direct Port Access DPA, Extended Voltage Mode

Intel® 31244 PCI-X to Serial ATA Controller

Intel® 31244 PCI-X to Serial ATA Controller Interface Ports

5.4Serial ATA Interface

Four 1.5 Gbits/s Serial ATA ports are located on the GD31244, to support point-to-point connectivity to disk drives, CDROMs, DVD ROMs or any other Serial ATA target device. Each port is compliant with the “Serial ATA: High speed Serialized AT Attachment Specification, Revision 1.0e. High-speed differential duplex serial lines send 8B/10B encoded data to and from the GD31244 and the target at a maximum raw data rate of 1.2 Gbits/s (150 Mbytes/s). Copies of the targets Task File Registers are maintained on the GD31244 and transferred as needed to the target. The Serial ATA protocol is software compatible with all existing operating systems that support ATA devices, however, performance and reliability are improved since all data is CRC checked.

5.4.1Direct Port Access (DPA)

The SATA Direct Port Access architecture allows for independent control of the SATA devices. Unlike ATA master/slave configuration where only one drive may operate at a time, DPA allows multiple drivers to be accessed concurrently. In addition, each port supports its own DMA channel allowing each port to transfer data independently (between a device and memory).

The DPA mode does change the register layout from PCI IDE. Therefore, legacy device drivers do not support this mode. DPA requires the registers (including the Command Block, Control Block, DMA, and SATA superset) for each drive is available at all times. Instead of using I/O space, these registers are mapped to a single 4 KB block. Each port has 512 KB; the remaining 2048 KB are for the common port registers. The 4 KB block is mapped using one PCI BAR register.

5.4.2Extended Voltage Mode

The SATA voltages were designed primarily for a cable connection to the hard drives. In certain applications, such as NAS/SAN enclosures, the hard disk drives (HDD) are connected to a backplane, not a cable (typically in desktop systems). Due to the frequency of the SATA interface, the backplane creates a significant attenuation of the SATA signals. In an effort to simplify system designs, the GD31244 offers an extended voltage range to help alleviate this issue. This extended voltage range allows standard SATA HDD to be used with SATA backplanes.

The firmware may be place into the External Voltage Mode by setting bit 14 in PHY Configuration Register Address 140H to 1. This forces the firmware to operate with this extended voltage range.

Table 9.	Normal Voltage Mode
	Parameter	Description	Minimum	Maximum	Units
	VOUT	TXx output differential peak-to-peak voltage swing	400	600	mVp-p
	VIN	RXx input differential peak-to-peak voltage swing	325	600	mVp-p

Table 10.	Extended Voltage Mode
	Parameter	Description	Minimum	Maximum	Units
	VOUT	TXx output differential peak-to-peak voltage swing	800	2000	mVp-p
	∆∆VIN	RXx input differential peak-to-peak voltage swing	175	2000	mVp-p
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