SCSI Registers
4-65
Register: 0x3A
Scratch Byte Register (SBR)
Read/Write
SBR
Scratch Byte Register
[7:0]
This is a general purpose register. Apart from CPU
access, only register Read/Write and Memory Moves into
this register alter its contents. The default value of this
register is zero. This register is called the DMA Watchdog
Timer on previous LSI53C8XX family products.
Register: 0x3B
DMA Control (DCNTL)
Read/Write
CLSE
Cache Line Size Enable
7
Setting this bit enables the LSI53C1000 to sense and
react to cache line boundaries set up by the
or PCI
register,
whichever contains the smaller value. Clearing this bit
disables the cache line size logic.
PFF
Prefetch Flush
6
Setting this bit causes the prefetch unit to flush its
contents. This bit clears after the flush is complete.
PFEN
Prefetch Enable
5
Setting this bit enables an 8-Dword SCRIPTS instruction
prefetch unit. The prefetch unit, when enabled, fetches
8 Dwords of instructions and instruction operands in
bursts of 4 or 8 Dwords. Prefetching instructions allows
the LSI53C1000 to make more efficient use of the system
PCI bus, thus improving overall system performance. A
flush occurs whenever the PFF bit is set, on all transfer
control instructions (when the transfer conditions are
7
0
SBR
0
0
0
0
0
0
0
0
7
6
5
4
3
2
1
0
CLSE
PFF
PFEN
SSM
IRQM
STD
R
COM
0
0
0
0
0
0
0
0
Содержание LSI53C1000
Страница 6: ...vi Preface...
Страница 16: ...xvi Contents...
Страница 28: ...1 12 Introduction...
Страница 234: ...4 124 Registers...
Страница 314: ...6 40 Specifications This page intentionally left blank...
Страница 318: ...6 44 Specifications This page intentionally left blank...
Страница 344: ...6 70 Specifications This page intentionally left blank...
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...