AC162078 Microchip Technology, AC162078 Datasheet - Page 85

• Manufacturer Part Number: AC162078
• Description: HEADER INTRFC MPLAB ICD2 18F1330
• Manufacturer: Microchip Technology

Specifications of AC162078

• Accessory Type: Transition Header
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• For Use With/related Products: ICD2
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Not applicable / Not applicable

9.0
9.1
All PIC18 devices include an 8 x 8 hardware multiplier
as part of the ALU. The multiplier performs an unsigned
operation and yields a 16-bit result that is stored in the
Product register pair, PRODH:PRODL. The multiplier’s
operation does not affect any flags in the STATUS
register.
Making multiplication a hardware operation allows it to
be completed in a single instruction cycle. This has the
advantages of higher computational throughput and
reduced code size for multiplication algorithms and
allows the PIC18 devices to be used in many
applications previously reserved for digital signal
processors. A comparison of various hardware and
software multiply operations, along with the savings in
memory and execution time, is shown in Table 9-1.
9.2
Example 9-1 shows the instruction sequence for an 8 x 8
unsigned multiplication. Only one instruction is required
when one of the arguments is already loaded in the
WREG register.
Example 9-2 shows the sequence to do an 8 x 8 signed
multiplication. To account for the sign bits of the
arguments, each argument’s Most Significant bit (MSb)
is tested and the appropriate subtractions are done.
TABLE 9-1:
 2009 Microchip Technology Inc.
16 x 16 unsigned
8 x 8 unsigned
16 x 16 signed
8 x 8 signed
Routine
8 x 8 HARDWARE MULTIPLIER
Introduction
Operation
PERFORMANCE COMPARISON FOR VARIOUS MULTIPLY OPERATIONS
Without hardware multiply
Without hardware multiply
Without hardware multiply
Without hardware multiply
Hardware multiply
Hardware multiply
Hardware multiply
Hardware multiply
Multiply Method
Program
Memory
(Words)
13
33
21
28
52
35
1
6
EXAMPLE 9-1:
EXAMPLE 9-2:
MOVF
MULWF
MOVF
MULWF
BTFSC
SUBWF
MOVF
BTFSC
SUBWF
Cycles
(Max)
242
254
69
91
28
40
1
6
PIC18F1230/1330
ARG1, W
ARG2
ARG1, W
ARG2
ARG2, SB
PRODH, F
ARG2, W
ARG1, SB
PRODH, F
@ 40 MHz
24.2 s
25.4 s
100 ns
600 ns
6.9 s
9.1 s
2.8 s
4.0 s
8 x 8 UNSIGNED
MULTIPLY ROUTINE
8 x 8 SIGNED MULTIPLY
ROUTINE
;
; ARG1 * ARG2 ->
; PRODH:PRODL
; ARG1 * ARG2 ->
; PRODH:PRODL
; Test Sign Bit
; PRODH = PRODH
;
; Test Sign Bit
; PRODH = PRODH
;
@ 10 MHz
102.6 s
27.6 s
36.4 s
96.8 s
16.0 s
11.2 s
Time
400 ns
2.4 s
- ARG1
- ARG2
DS39758D-page 85
@ 4 MHz
242 s
254 s
69 s
91 s
28 s
40 s
1 s
6 s