LSI 53C810A - Manual (Page 180)

6-40 Instruction Set of the I/O Processor
operating register set of the chip. If it does, a PCI illegal read/write cycle
occur, the chip issues an interrupt (Illegal Instruction Detected)
immediately following.
The SIOM and DIOM bits in the DMA Mode (DMODE) register determine
whether the destination or source address of the instruction is in Memory
space or I/O space. The Load and Store utilizes the PCI commands for
I/O read and I/O write to access the I/O space.
6.8.1 First Dword
IT[2:0] Instruction Type [31:29]
These bits should be 111, indicating the Load and Store
instruction.
DSA DSA Relative 28
When this bit is cleared, the value in the DMA SCRIPTS
Pointer Save (DSPS) is the actual 32-bit memory address
used to perform the Load and Store to/from. When this
bit is set, the chip determines the memory address to
perform the Load and Store to/from by adding the 24-bit
signed offset value in the
DMA SCRIPTS Pointer Save
(DSPS) to the Data Structure Address (DSA) .
R Reserved [27:26]
NF No Flush (Store instruction only) 25
When this bit is set, the LSI53C810A performs a Store
without flushing the prefetch unit. When this bit is cleared,
the Store instruction automatically flushes the prefetch
unit. Use No Flush if the source and destination are not
within four instructions of the current Store instruction.
Bits A1, A0 Number of Bytes Allowed to Load/Store
00 One, two, three or four
01 One, two, or three
10 One or two
11 One