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Instruction Set of the I/O Processor
Read/Write Instructions
6-14
SYM53C810A Data Manual
Read/Write Instructions
T he Read/Write Instruction type moves the con-
tents of one register to another, or performs arith-
metic operations such as AND, OR, X OR,
Addition, and Shift. Figure 6-4 illustrates the reg-
ister bit values that represent a Read/Write instruc-
tion.
First Dword
Bits 31-30 Instruction Type - Read/Write
Instruction
T he Read/Write instruction uses operator bits
26 through 24 in conjunction with the op code
bits to determine which instruction is currently
selected.
Bits 29-27 Op Code
T he combinations of these bits determine if the
instruction is a Read/Write or an I/O instruc-
tion. Op codes 000 through 100 are considered
I/O instructions. Refer to Table 6-1 for field
definitions.
Bits 26-24 Operator
T hese bits are used in conjunction with the op
code bits to determine which instruction is
currently selected. Refer to Table 6-1 for field
definitions.
Bits 22-16 Register Address - A(6-0)
Register values may be changed from
SCRIPT S in read-modify-write cycles or move
to/from SFBR cycles. A(6-0) select an 8-bit
source/destination register within the
SYM53C810A.
Second Dword
Bits 31-0 Destination Address
T his field contains the 32-bit destination
address where the data is to be moved.
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.
T he Add operation can be used to increment or
decrement register values (or memory values if
used in conjunction with a Memory-to-Register
Move operation) for use as loop counters.
Move to/from
SFBR Cycles
All operations are read-modify-writes. However,
two registers are involved, one of which is always
the SFBR. T he possible functions of this instruc-
tion are:
I
Write one byte (value contained within the
SCRIPT S instruction) into any chip register.
I
Move to/from the SFBR from/to any other
register.
I
Alter the value of a register with AND/OR/
ADD/X OR/SHIFT LEFT /SHIFT RIGHT
operators.
I
After moving values to the SFBR, the compare
and jump, call, or similar instructions may be
used to check the value.
I
A Move-to-SFBR followed by a Move-from-
SFBR can be used to perform a register to
register move.