tailieunhanh - Embedded FreeBSD Cookbook phần 10

Ba byte tiếp theo chứa bắt đầu của phân vùng đầu, khu vực, định dạng hình trụ. Đĩa truyền thống truy cập lưu trữ bằng xi lanh, khu vực đầu và bù đắp. Với sự gia tăng liên tục trong khả năng của ổ đĩa cứng, không gian dành riêng trong MBR trở nên quá nhỏ để giải quyết một ổ đĩa cứng hoàn toàn. | 211 Appendix B PCI The subsequent sections describe each mandatory PCI configuration register that is implemented by all PCI devices. The most notable for device driver writers are the vendor ID and device ID registers. These registers are used to determine if the physical device is installed in the system. Vendor ID Register The Vendor ID Register is a 16-bit register that contains a unique value identifying the device manufacturer. Every PCI manufacturer registers with the PCI SIG to obtain a unique Vendor ID. The Measurement Computing Vendor ID is hexadecimal 1307. Device ID Register The Device ID register is a 16-bit register that contains a unique value defined by the manufacturer for this PCI device. The PCI-DIO24 Device ID is hexadecimal 28. Command Register The command register is a 16-bit register that provides control over the device s ability to respond to PCI accesses. Currently only bits 0 9 are defined. Each of the defined bits represents a capability. The PCI designer sets the bits that are implemented by the device. The bits are defined as follows Bit Function 0 IO Access Enable 1 Memory Access Enable 2 Master Enable 3 Special Cycle Recognition 4 Memory Write and Invalidate Enable 5 VGA Palette Snoop Enable 6 Parity Error Response 7 Wait Cycle Enable 8 System Error Enable 9 Fast Back-to-Back Enable 10 15 Reserved 212 Embedded FreeBSD Cookbook Status Register The Status Register is a 16-bit register that provides the device status. The bits are defined in the status register as follows Bit Function 0 4 Reserved 5 66 MHz Capable 6 UDF Supported 7 Fast Back-to-Back Capable 8 Data Parity Reported 9 10 Device Select 11 Signaled Target Abort 12 Received Target Abort 13 Received Master Abort 14 Signaled System Error 15 Detected Parity Error Revision ID The revision ID register contains an 8-bit value assigned by the manufacturer that contains the device revision number. Class Code The class code register is a 24-bit register that defines the base class .