
SCSI Functional Description
2-37
CRC Request Pending
SCSI Control Zero
(SCNTL0)
, Bit 2
This bit indicates it is acceptable to force a CRC
request. This bit will only be clear when a CRC request
has been sent and no data has been transferred since
the request. This bit may be used to prevent
back-to-back CRC conditions.
This bit is set to cause internal logic not to check or
report CRC errors during Ultra3 transfers.
This bit is set to cause the device to not check for a
CRC request prior to a phase change on the SCSI bus.
This condition normally causes a SCSI error condition.
Note: Setting this bit makes the SYM53C1010
noncompliant to the SPI-3 specification. This bit should
not be set under normal operating conditions.
When set, this bit resets the internal CRC interval
counter to zero.
These bits determine when a CRC request is sent out
by the device. The interval is only applicable when the
device is operating in target mode and transferring data
in DT Data-In or DT Data-Out phases. The intervals are
provided, in bytes, as: 0x0 = disabled; 0x1 = 128; 0x2 =
256; 0x3 = 512; ... ; 0x9 = 32768; 0xA = 65536;
0xB–0xF = Reserved.
Disable CRC Checking
CRC Control Zero
(CRCCNTL0)
, Bit 7
CRC Control Zero
(CRCCNTL0)
, Bit 6
Disable CRC Protocol
Checking
CRC Reset Counter
(Target Mode Only)
CRC Interval Counter
(Target Mode Only)
CRC Control Zero
(CRCCNTL0)
, Bit 5
CRC Control Zero
(CRCCNTL0)
, Bits
[3:0]
Table 2.6
SCSI Parity Errors and Interrupts
DHP
1
1. DHP = Disable Halt on SATN/ or Parity Error (bit 5,
SCSI Control One (SCNTL1)
)
2. PAR = Parity Error (bit 0
SCSI Interrupt Enable One (SIEN1)
)
PAR
2
Description
0
0
Halts when a parity error occurs in the target or initiator mode and
does NOT generate an interrupt.
0
1
Halts when a parity error occurs in the target mode and generates
an interrupt in the target or initiator mode.
1
0
Does not halt in target mode when a parity error occurs until the
end of the transfer. An interrupt is not generated.
1
1
Does not halt in target mode when a parity error occurs until the
end of the transfer. An interrupt is generated.
Table 2.5
Bits Used for Parity/CRC/AIP Control and Generation (Cont.)
Bit Name
Location
Description