PIC24HJ32GP302_11 Datasheet, PDF (24/368 Pages) Microchip Technology – High-Performance, 16-bit Microcontrollers

PIC24HJ32GP302/304, PIC24HJ64GPX02/X04 AND PIC24HJ128GPX02/X04
3.5 Arithmetic Logic Unit (ALU)
The PIC24HJ32GP302/304, PIC24HJ64GPX02/X04
and PIC24HJ128GPX02/X04 ALU is 16 bits wide and
is capable of addition, subtraction, bit shifts and logic
operations. Unless otherwise mentioned, arithmetic
operations are two’s complement in nature. Depending
on the operation, the ALU can affect the values of the
Carry (C), Zero (Z), Negative (N), Overflow (OV) and
Digit Carry (DC) Status bits in the SR register. The C
and DC Status bits operate as Borrow and Digit Borrow
bits, respectively, for subtraction operations.
The ALU can perform 8-bit or 16-bit operations,
depending on the mode of the instruction that is used.
Data for the ALU operation can come from the W
register array or data memory, depending on the
addressing mode of the instruction. Likewise, output
data from the ALU can be written to the W register array
or a data memory location.
For information on the SR bits affected by each instruc-
tion, refer to the “16-bit MCU and DSC Programmer’s
Reference Manual” (DS70157).
The PIC24HJ32GP302/304, PIC24HJ64GPX02/X04
and PIC24HJ128GPX02/X04 CPU incorporates
hardware support for both multiplication and division.
This includes a dedicated hardware multiplier and
support hardware for 16-bit-divisor division.
3.5.1 MULTIPLIER
Using the high-speed 17-bit x 17-bit multiplier, the ALU
supports unsigned, signed or mixed-sign operation in
several MCU multiplication modes:
• 16-bit x 16-bit signed
• 16-bit x 16-bit unsigned
• 16-bit signed x 5-bit (literal) unsigned
• 16-bit unsigned x 16-bit unsigned
• 16-bit unsigned x 5-bit (literal) unsigned
• 16-bit unsigned x 16-bit signed
• 8-bit unsigned x 8-bit unsigned
3.5.2 DIVIDER
The divide block supports 32-bit/16-bit and 16-bit/16-bit
signed and unsigned integer divide operations with the
following data sizes:
• 32-bit signed/16-bit signed divide
• 32-bit unsigned/16-bit unsigned divide
• 16-bit signed/16-bit signed divide
• 16-bit unsigned/16-bit unsigned divide
The quotient for all divide instructions ends up in W0
and the remainder in W1. 16-bit signed and unsigned
DIV instructions can specify any W register for both
the 16-bit divisor (Wn) and any W register (aligned)
pair (W(m + 1):Wm) for the 32-bit dividend. The divide
algorithm takes one cycle per bit of divisor, so both
32-bit/16-bit and 16-bit/16-bit instructions take the
same number of cycles to execute.
3.5.3 MULTI-BIT DATA SHIFTER
The multi-bit data shifter is capable of performing up to
16-bit arithmetic or logic right shifts, or up to 16-bit left
shifts in a single cycle. The source can be either a
working register or a memory location.
The shifter requires a signed binary value to determine
both the magnitude (number of bits) and direction of the
shift operation. A positive value shifts the operand right.
A negative value shifts the operand left. A value of ‘0’
does not modify the operand.
DS70293E-page 24
© 2011 Microchip Technology Inc.