LSI LSI53C895A, Technical Manual

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SCSI Registers 4-71
The IRQ/ output is latched. Once asserted, it will remain asserted until
the interrupt is cleared by reading the appropriate status register.
Masking an interrupt after the IRQ/ output is asserted does not cause
deassertion of IRQ/.
For more information on interrupts, see Chapter 2, “Functional
Description.”
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 LSI53C895A to sense and
react to cache line boundaries set up by the
DMA Mode
(DMODE) or PCI Cache Line Size register, whichever
contains the smaller value. Clearing this bit disables the
cache line size logic and the LSI53C895A monitors the
cache line size using the DMODE register.
PFF Prefetch Flush 6
Setting this bit causes the prefetch unit to flush its
contents. The bit clears after the flush is complete.
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 IRQD COM
0 0 0 0 0 0 0 0