Register: 0x1B

Chip Test Three (CTEST3)

Read/Write

7

 

 

 

4

 

3

 

2

1

0

 

 

V

 

 

FLF

 

CLF

FM

WRIE

 

 

 

 

 

 

 

 

 

 

 

x

x

 

x

x

 

0

 

0

0

0

 

 

 

 

 

 

 

 

 

 

 

V

 

Chip Revision Level

 

 

 

 

[7:4]

 

 

These bits identify the chip revision level for software

 

 

purposes. It should have the same value as the lower

 

 

nibble of the PCI Revision ID (Rev ID) register, at address

 

 

0x08 in the configuration space.

 

 

 

FLF

 

Flush DMA FIFO

 

 

 

 

3

When this bit is set, data residing in the DMA FIFO is transferred to memory, starting at the address in the DMA Next Address 64 (DNAD64) register. The internal DMAWR signal, controlled by the Chip Test Five (CTEST5) register, determines the direction of the transfer. This bit is not self-clearing; clear it once the data is successfully transferred by the LSI53C875A.

Note:

Polling of FIFO flags is allowed during flush operations.

 

CLF

Clear DMA FIFO

2

 

When this bit is set, all data pointers for the DMA FIFO

 

are cleared. Any data in the FIFO is lost. After the

 

 

LSI53C875A successfully clears the appropriate FIFO

 

 

pointers and registers, this bit automatically clears.

 

Note:

This bit does not clear the data visible at the bottom of the

 

FIFO.

 

FM

Fetch Pin Mode

1

 

When set, this bit causes the FETCH/ pin to deassert

 

 

during indirect and table indirect read operations.

 

 

FETCH/ is only active during the opcode portion of an

 

instruction fetch. This allows the storage of SCRIPTS in a PROM while data tables are stored in RAM.

If this bit is not set, FETCH/ is asserted for all bus cycles during instruction fetches.

4-56Registers

Page 148
Image 148
LSI 53C875A technical manual Register 0x1B, Flf, Clf