32-Bit Hardware Multiplier Operation
9-6
32-Bit Hardware Multiplier
Table 9−3. OP2 registers
OP2 Register Name Operation
OP2
Start multiplication with 16-bit wide operand two OP2
(operand bits 0 up to 15)
OP2L
Start multiplication with 32-bit wide operand two OP2
(operand bits 0 up to 15)
OP2H
Continue multiplication with 32-bit wide operand two OP2
(operand bits 16 up to 31)
For 8-bit or 24-bit operands the operand registers can be accessed with byte
instructions. Accessing the multiplier with a byte instruction during a signed
operation will automatically cause a sign extension of the byte within the
multiplier module. For 24-bit operands only the high word should be written as
byte. Whether or not the 24-bit operands are sign extended is defined by the
register that is used to write the low word, because this register defines if the
operation is unsigned or signed.
The high word of a 32-bit operand remains unchanged when changing the size
of the operand to 16 bit either by modifying the operand size bits or by writing
to the respective operand register. During the execution of the 16-bit operation
the content of the high word is ignored.
Note: Changing of First or Second Operand During Multiplication
Changing OP1 or OP2 while the selected multiply operation is being
calculated will render any results invalid that are not ready at the time the new
operand(s) are changed.
Writing OP2 or OP2L will abort any ongoing calculation and start a new
operation. Results that are not ready at that time are invalid also for following
MAC or MACS operations.
Refer to the tables “Result Availability” for the different modes on how many
CPU cycles are needed until a certain result register is ready and valid.
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