70592C Datasheet, PDF (32/314 Pages) Microchip Technology – High-Performance, 16-bit Microcontrollers

PIC24HJXXXGPX06A/X08A/X10A
3.4 Arithmetic Logic Unit (ALU)
The PIC24HJXXXGPX06A/X08A/X10A ALU is 16 bits
wide and is capable of addition, subtraction, bit shifts
and logic operations. Unless otherwise mentioned,
arithmetic operations are 2’s complement in nature.
Depending on the operation, the ALU may 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 reg-
ister array, or data memory, depending on the address-
ing mode of the instruction. Likewise, output data from
the ALU can be written to the W register array or a data
memory location.
Refer to the “16-bit MCU and DSC Programmer’s
Reference Manual” (DS70157) for information on the
SR bits affected by each instruction.
The PIC24HJXXXGPX06A/X08A/X10A CPU
incorporates hardware support for both multiplication
and division. This includes a dedicated hardware
multiplier and support hardware for 16-bit divisor
division.
3.4.1 MULTIPLIER
Using the high-speed 17-bit x 17-bit multiplier, the ALU
supports unsigned, signed or mixed-sign operation in
several 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
3.4.2 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. Sixteen-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.
3.4.3 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.
DS70592C-page 32
© 2011 Microchip Technology Inc.