LSI 53C875A - Manual (Page 138)

4-46 Registers
Register: 0x0F
SCSI Status Two (SSTAT2)
Read Only
ILF1 SIDL Most Significant Byte Full 7
This bit is set when the most significant byte in the SCSI
Input Data Latch (SIDL) contains data. Data is transferred
from the SCSI bus to the SCSI Input Data Latch register
before being sent to the DMA FIFO and then to the host
bus. The SIDL register contains SCSI data received
asynchronously. Synchronous data received does not
flow through this register.
ORF1 SODR Most Significant Byte Full 6
This bit is set when the most significant byte in the SCSI
Output Data register (SODR, a hidden buffer register
which is not accessible) contains data. The SODR
register is used by the SCSI logic as a second storage
register when sending data synchronously. It is not
accessible to the user. This bit is used to determine how
many bytes reside in the chip when an error occurs.
OLF1 SODL Most Significant Byte Full 5
This bit is set when the most significant byte in the SCSI
Output Data Latch (SODL) contains data. The SODL
register is the interface between the DMA logic and the
SCSI bus. In synchronous mode, data is transferred from
the host bus to the SODL register, and then to the SCSI
Output Data register (SODR, a hidden buffer register
which is not accessible) before being sent to the SCSI
bus. In asynchronous mode, data is transferred from the
host bus to the SODL register, and then to the SCSI bus.
The SODR buffer register is not used for asynchronous
transfers. It is possible to use this bit to determine how
many bytes reside in the chip when an error occurs.
FF4 FIFO Flags, Bit 4 4
This is the most significant bit in the SCSI FIFO Flags
field, when concatenated with bits [7:4] (FF[3:0]) in
SCSI
Status One (SSTAT1) . For a complete description of this
7 6 5 4 3 2 1 0
ILF1 ORF1 OLF1 FF4 SPL1 R LDSC SDP1
0 0 0 0 x x 1 x