
4-36
Registers
Notime
Selection Time-out Disable
Setting this bit disables the 250 ms timer for all modes,
including byte-to-byte. If STO is disabled, the user cannot
abort a Select/Reselect SCRIPTS instruction using the
ABORT bit.
4
DFP
DMA FIFO Parity
This bit represents the parity bit of the DMA FIFO when
reading data out of the DMA FIFO using programmed I/O.
In order to transfer data to or from the DMA FIFO,
perform a read or a write to the
Chip Test Six (CTEST6)
register. When loading data into the FIFO using
programmed I/O, write this bit to the FIFO as the parity
bit for each byte loaded. When writing data to the DMA
FIFO, set this bit with the status of the parity bit to be
written to the FIFO before writing the byte to the FIFO.
3
EVP
Even Parity
Parity is generated for all slave mode register reads and
master mode memory writes. This bit controls the parity
sense.
2
Setting this bit causes the SYM53C710 to generate even
parity when driving data on the host data bus. The
SYM53C710 inverts the parity bit received from the SCSI
bus to create even parity. In addition, the even parity
received from the host bus is inverted to odd parity before
the SYM53C710 checks parity and sends the data to the
SCSI bus. Clearing this bit causes the SYM53C710 to
maintain odd parity throughout the chip.
TT1
Transfer Type Bit
The inverted value of this bit is asserted on the TT1 pin
during bus mastership in Bus Mode 2 only. This bit is not
used in Bus Mode 1.
1
DIFF
Differential Mode
Setting this bit enables the SYM53C710 to interface with
external differential pair transceivers. The SCSI BSY/,
SEL/, and RST/ are input only in differential mode. For
more information on differences between the two modes,
refer to the pin descriptions for these signals. Resetting
this bit enables SE mode. This bit should be set in the
initialization routine if the differential pair interface is to be
used.
0