2-30
Functional Description
–
Bit 5, ENAS (Enable CRC Auto Seed), is set to cause the CRC
logic to automatically reseed itself after every CRC check
performed during DT Data In SCSI transfers. When this bit is
cleared, the SCSI control logic controls when the CRC logic is
reseeded.
–
Bit 4, TSTSD (Test CRC Seed), is set to cause the CRC logic to
immediately reseed itself. Do not set this bit during normal
operation as it may cause corrupt CRCs to be generated.
–
Bit 3, TSTCHK (Test CRC Check), is set to cause the CRC logic
to initiate a CRC check. Do not set this bit during normal
operation as it creates spurious CRC errors.
–
Bit 2, TSTADD (Test CRC Accumulate), is set to cause the CRC
block to include the value present in the input register in the
current CRC calculation. A new output CRC value results. Do not
set this bit during normal operation as corrupt CRC values result.
–
Bits [1:0], CRCDSEL[1:0] (CRC Data Register Selector), control
the data visible in the CRC Data register.
•
The
register:
–
Bits [31:0] CRCDATA (CRC Data). The value in this register is
dependent upon the setting of the CRCDSEL bits.
2.2.5.5 Using the SCSI Clock Quadrupler
The LSI53C1000 can quadruple the frequency of a 40 MHz SCSI clock,
allowing the system to perform Ultra160 SCSI transfers. This option is
user-selectable with bit settings in the
, and
registers. At
power-on or reset, the quadrupler is disabled and powered down. Follow
these steps to use the clock quadrupler:
1.
Set the SCLK Quadrupler Enable bit (
register, bit 3).
2.
Do not poll bit 5 of the
register. Bit 5 is
reserved. Use a delay of 50
µ
s after the quadrupler enable bit is set
in step 1.
3.
Halt the SCSI clock by setting the Halt SCSI Clock bit (
register, bit 5).
Содержание LSI53C1000
Страница 6: ...vi Preface...
Страница 16: ...xvi Contents...
Страница 28: ...1 12 Introduction...
Страница 234: ...4 124 Registers...
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Страница 318: ...6 44 Specifications This page intentionally left blank...
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Страница 350: ...6 76 Specifications Figure 6 42 LSI53C1000 329 Ball Grid Array Bottom view...
Страница 352: ...6 78 Specifications...
Страница 360: ...A 8 Register Summary...
Страница 376: ...IX 12 Index...