PIC18C858-E/L Microchip Technology, PIC18C858-E/L Datasheet - Page 46

• Manufacturer Part Number: PIC18C858-E/L
• Description: IC MCU OTP 16KX16 CAN 84PLCC
• Manufacturer: Microchip Technology
• Series: PIC® 18Cr

Specifications of PIC18C858-E/L

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: CAN, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LVD, POR, PWM, WDT
• Number Of I /o: 68
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: OTP
• Ram Size: 1.5K x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 16x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 84-PLCC
• For Use With: AC164310 - MODULE SKT FOR PM3 84PLCCDVA18XL840 - ADAPTER DEVICE ICE 84PLCCAC174012 - MODULE SKT PROMATEII 84PLCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Other names: PIC18C858E/L

PIC18CXX8
4.6
An “Instruction Cycle” consists of four Q cycles (Q1,
Q2, Q3 and Q4). The instruction fetch and execute are
pipelined such that fetch takes one instruction cycle
while decode and execute takes another instruction
cycle. However, due to the pipelining, each instruction
effectively executes in one cycle. If an instruction
causes the program counter to change (e.g., GOTO),
two cycles are required to complete the instruction
(Example 4-2).
A fetch cycle begins with the program counter (PC)
incrementing in Q1.
In the execution cycle, the fetched instruction is latched
into the “Instruction Register” (IR) in cycle Q1. This
instruction is then decoded and executed during the
Q2, Q3, and Q4 cycles. Data memory is read during Q2
(operand read) and written during Q4 (destination
write).
EXAMPLE 4-2:
TABLE 4-1:
DS30475A-page 46
—
MOVLW 055h
GOTO 000006h
MOVFF 123h, 456h
—
1. MOVLW 55h
2. MOVWF PORTB
3. BRA SUB_1
4. BSF
5. Instruction @ address SUB_1
All instructions are single cycle, except for any program branches. These take two cycles since the fetch
instruction is “flushed” from the pipeline while the new instruction is being fetched and then executed.
Instruction Flow/Pipelining
PORTA, BIT3 (Forced NOP)
Instruction
INSTRUCTIONS IN PROGRAM MEMORY
INSTRUCTION PIPELINE FLOW
Fetch 1
T
CY
0
0E55h
EF03h, F000h
C123h, F456h
Advanced Information
Execute 1
Fetch 2
Opcode
T
CY
1
Execute 2
Fetch 3
T
CY
2
4.7
The program memory is addressed in bytes. Instruc-
tions are stored as two bytes or four bytes in program
memory. The Least Significant Byte of an instruction
word is always stored in a program memory location
with an even address (LSB = ’0’). Figure 4-1 shows an
example of how instruction words are stored in the pro-
gram memory. To maintain alignment with instruction
boundaries, the PC increments in steps of 2 and the
LSB will always read ’0’ (See Section 4.4).
The CALL and GOTO instructions have an absolute pro-
gram memory address embedded into the instruction.
Since instructions are always stored on word bound-
aries, the data contained in the instruction is a word
address. The word address is written to PC<20:1>,
which accesses the desired byte address in program
memory. Instruction #2 in Figure 4-1 shows how the
instruction “GOTO 000006h” is encoded in the program
memory. Program branch instructions that encode a rel-
ative address offset operate in the same manner. The
offset value stored in a branch instruction represents the
number of single word instructions by which the PC will
be offset. Section 23.0 provides further details of the
instruction set.
Execute 3
Fetch 4
Instructions in Program Memory
Memory
T
CY
EFh
C1h
0Eh
03h
00h
F0h
23h
56h
F4h
55h
3
Fetch SUB_1 Execute SUB_1
Flush
T
 2000 Microchip Technology Inc.
CY
4
Address
00000Ah
00000Bh
00000Ch
00000Dh
00000Eh
000007h
000008h
000009h
00000Fh
000010h
000012h
000011h
T
CY
5