LSI 53C810A - Manual (Page 163)

Read/Write Instructions 6-23
6.5 Read/Write Instructions
The Read/Write instruction type moves the contents of one register to
another, or performs arithmetic operations such as AND, OR, XOR,
Addition, and Shift.
6.5.1 First Dword
IT[1:0] Instruction Type - Read/Write Instruction [31:30]
The Read/Write instruction uses operator bits 26 through
24 in conjunction with the opcode bits to determine which
instruction is currently selected.
OPC[2:0] OpCode [29:27]
The combinations of these bits determine if the
instruction is a Read/Write or an I/O instruction. Opcodes
0b000 through 0b100 are considered I/O instructions.
Refer to
Table 6.2 for field definitions.
O[2:0] Operator [26:24]
These bits are used in conjunction with the opcode bits
to determine which instruction is currently selected. Refer
to
Table 6.2 for field definitions.
A[6:0] Register Address - A[6:0] [22:16]
It is possible to change register values from SCRIPTS in
read-modify-write cycles or move to/from SFBR cycles.
A[6:0] select an 8-bit source/destination register within
the LSI53C810A.
6.5.2 Second Dword
Destination Address [31:0]
This field contains the 32-bit destination address where
the data is to move.
6.5.3 Read-Modify-Write Cycles
During these cycles the register is read, the selected operation is
performed, and the result is written back to the source register.