PIC24HJ128GP206-I Datasheet, PDF (23/286 Pages) Microchip Technology – High-Performance, 16-Bit Microcontrollers

PIC24HJXXXGPX06/X08/X10
2.4 Arithmetic Logic Unit (ALU)
The PIC24HJXXXGPX06/X08/X10 ALU is 16 bits wide
and is capable of addition, subtraction, bit shifts and
logic operations. Unless otherwise mentioned, arith-
metic 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), Over-
flow (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 oper-
ations.
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 “dsPIC30F/33F Programmer’s Reference
Manual” (DS70157) for information on the SR bits
affected by each instruction.
The PIC24HJXXXGPX06/X08/X10 CPU incorporates
hardware support for both multiplication and division.
This includes a dedicated hardware multiplier and sup-
port hardware for 16-bit divisor division.
2.4.1 MULTIPLIER
Using the high-speed 17-bit x 17-bit multiplier, the ALU
supports unsigned, signed or mixed-sign operation in
several multiplication modes:
1. 16-bit x 16-bit signed
2. 16-bit x 16-bit unsigned
3. 16-bit signed x 5-bit (literal) unsigned
4. 16-bit unsigned x 16-bit unsigned
5. 16-bit unsigned x 5-bit (literal) unsigned
6. 16-bit unsigned x 16-bit signed
7. 8-bit unsigned x 8-bit unsigned
2.4.2 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:
1. 32-bit signed/16-bit signed divide
2. 32-bit unsigned/16-bit unsigned divide
3. 16-bit signed/16-bit signed divide
4. 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.
2.4.3 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.
© 2007 Microchip Technology Inc.
DS70175F-page 21