Registers: 0x09–0x0B

Class Code

Read Only

23

0

CC

0 0 0 0 0

0 0 1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CCClass Code[23:0]

This 24-bit register is used to identify the generic function of the device. The upper byte of this register is a base class code, the middle byte is a subclass code, and the lower byte identifies a specific register level programming interface. The value of this register is 0x010000, which identifies a SCSI controller.

Register: 0x0C

Cache Line Size

Read/Write

7

0

CLS

0

0

0

0

0

0

0

0

CLSCache Line Size[7:0]

This register specifies the system cache line size in units of 32-bit words. The value in this register is used by the device to determine whether to use Write and Invalidate or Write commands for performing write cycles, and whether to use Read, Read Line, or Read Multiple commands for performing read cycles as a bus master. Devices participating in the caching protocol use this field to know when to retry burst accesses at cache line boundaries. These devices can ignore the PCI cache support lines (SDONE and SB0/) when this register is cleared to 0. If this register is programmed to a number which is not a power of 2, the device will not use PCI performance commands to perform data transfers.

PCI Configuration Registers

4-7

Page 99
Image 99
LSI 53C875A technical manual Registers 0x09-0x0B, Register 0x0C