PIC18F6585-I/L Microchip Technology, PIC18F6585-I/L Datasheet - Page 109

• Manufacturer Part Number: PIC18F6585-I/L
• Description: Microcontrollers (MCU) 48KB 3328 RAM 52 I/O
• Manufacturer: Microchip Technology

Specifications of PIC18F6585-I/L

• Processor Series: PIC18F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 3.25 KB
• Interface Type: I2C/SPI/AUSART/CAN
• Maximum Clock Frequency: 40 MHz
• Number Of Programmable I/os: 53
• Number Of Timers: 5
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734, 52712-325, EWPIC18
• Development Tools By Supplier: PG164130, DV164035, DV244005, DV164005, PG164120, ICE2000, ICE4000, DV164136, DM183032
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 12-ch x 10-bit
• Program Memory Type: Flash
• Program Memory Size: 48 KB
• Package / Case: PLCC-68
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.0
8.1
An 8 x 8 hardware multiplier is included in the ALU of
the PIC18F6585/8585/6680/8680 devices. By making
the multiply a hardware operation, it completes in a sin-
gle instruction cycle. This is an unsigned multiply that
gives a 16-bit result. The result is stored in the 16-bit
product register pair (PRODH:PRODL). The multiplier
does not affect any flags in the ALUSTA register.
Making the 8 x 8 multiplier execute in a single cycle
gives the following advantages:
• Higher computational throughput
• Reduces code size requirements for multiply
The performance increase allows the device to be used
in applications previously reserved for Digital Signal
Processors.
Table 8-1 shows a performance comparison between
enhanced devices using the single-cycle hardware
multiply and performing the same function without the
hardware multiply.
TABLE 8-1:
 2004 Microchip Technology Inc.
8 x 8 unsigned
8 x 8 signed
16 x 16 unsigned
16 x 16 signed
algorithms
Routine
8 x 8 HARDWARE MULTIPLIER
Introduction
PERFORMANCE COMPARISON
Without hardware multiply
Without hardware multiply
Without hardware multiply
Without hardware multiply
Hardware multiply
Hardware multiply
Hardware multiply
Hardware multiply
Multiply Method
PIC18F6585/8585/6680/8680
Program
Memory
(Words)
13
33
21
24
52
36
1
6
8.2
Example 8-1 shows the sequence to do an 8 x 8
unsigned multiply. Only one instruction is required
when one argument of the multiply is already loaded in
the WREG register.
Example 8-2 shows the sequence to do an 8 x 8 signed
multiply. To account for the sign bits of the arguments,
each argument’s Most Significant bit (MSb) is tested
and the appropriate subtractions are done.
EXAMPLE 8-1:
EXAMPLE 8-2:
MOVF
MULWF
MOVF
MULWF
BTFSC
SUBWF
MOVF
BTFSC
SUBWF
Cycles
(Max)
242
254
69
91
24
36
1
6
Operation
ARG1, W
ARG2
ARG1, W
ARG2
ARG2, SB
PRODH
ARG2, W
ARG1, SB
PRODH
@ 40 MHz
24.2 s
25.4 s
100 ns
600 ns
6.9 s
9.1 s
2.4 s
3.6 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
14.4 s
27.6 s
36.4 s
96.8 s
Time
400 ns
2.4 s
9.6 s
DS30491C-page 107
- ARG1
- ARG2
@ 4 MHz
242 s
254 s
69 s
91 s
24 s
36 s
1 s
6 s