LSI LSI53C895A, Technical Manual

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5-6 SCSI SCRIPTS Instruction Set
5.3.1 First Dword
IT[1:0] Instruction Type - Block Move [31:30]
The IT bit configuration (00) defines a Block Move
Instruction Type.
IA Indirect Addressing 29
This bit determines if addressing is direct or indirect.
If IA bit is (0), use destination field as an address (direct
addressing). If IA bit is (1), use destination field as a
pointer to an address (indirect addressing).
When this bit is zero, user data is moved to or from the
32-bit data start address for the Block Move instruction.
The value is loaded into the chip’s address register and
incremented as data is transferred. The address of the
data to move is in the second Dword of this instruction.
When this bit is one, the 32-bit user data start address
for the Block Move is the address of a pointer to the
actual data buffer address. The value at the 32-bit start
address is loaded into the chip’s
DMA Next Address
(DNAD) register using a third longword fetch (4-byte
transfer across the host computer bus).
Direct Addressing
The byte count and absolute address are:
Indirect Addressing
Use the fetched byte count, but fetch the data address
from the address in the instruction.
31 30 29 28 27 26 24 23 16 15 8 7 0
DMA Command (DCMD) Register DMA Byte Counter (DBC) Register
IT[1:0] IA TIA OPC SCSIP[2:0] Transfer Counter [23:0]
0 0 x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x
Command Byte Count
Address of Data
Command Byte Count
Address of Pointer to Data