may transfer up to three additional bytes before halting to synchronize between internal core cells. During synchronous operation, the LSI53C875A transfers data until there are no outstanding synchronous offsets. If the LSI53C875A is receiving data, any data residing in the DMA FIFO is sent to memory before halting.

When this bit is set, the LSI53C875A does not halt the SCSI transfer when SATN/ or a parity error is received.

CON

Connected

4

 

This bit is automatically set any time the LSI53C875A is

 

connected to the SCSI bus as an initiator or as a target.

 

It is set after the LSI53C875A successfully completes

 

 

arbitration or when it has responded to a bus initiated

 

 

selection or reselection. This bit is also set after the chip

 

wins simple arbitration when operating in low level mode.

 

When this bit is cleared, the LSI53C875A is not

 

 

connected to the SCSI bus.

 

 

The CPU can force a connected or disconnected

 

 

condition by setting or clearing this bit. This feature is

 

 

used primarily during loopback mode.

 

RST

Assert SCSI RST/ Signal

3

 

Setting this bit asserts the SRST/ signal. The SRST/

 

 

output remains asserted until this bit is cleared. The

 

 

25 s minimum assertion time defined in the SCSI

 

 

specification must be timed out by the controlling

 

 

microprocessor or a SCRIPTS loop.

 

AESP

Assert Even SCSI Parity (force bad parity)

2

 

When this bit is set, the LSI53C875A asserts even parity.

 

It forces a SCSI parity error on each byte sent to the

 

 

SCSI bus from the chip. If parity checking is enabled,

 

 

then the LSI53C875A checks data received for odd parity.

 

This bit is used for diagnostic testing and is cleared for

 

 

normal operation. It is useful to generate parity errors to

 

test error handling functions.

 

IARB

Immediate Arbitration

1

 

Setting this bit causes the SCSI core to immediately

 

 

begin arbitration once a Bus Free phase is detected

 

following an expected SCSI disconnect. This bit is useful for multithreaded applications. The ARB[1:0] bits in the

4-24Registers

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LSI 53C875A technical manual Con, Rst, Aesp, Iarb