PIC12C671/JW Microchip Technology, PIC12C671/JW Datasheet - Page 10

• Manufacturer Part Number: PIC12C671/JW
• Description: IC MCU EPROM 1KX14 A/D 8CDIP
• Manufacturer: Microchip Technology
• Series: PIC® 12Cr

Specifications of PIC12C671/JW

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 10MHz
• Peripherals: POR, WDT
• Number Of I /o: 5
• Program Memory Size: 1.75KB (1K x 14)
• Program Memory Type: EPROM, UV
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 5.5 V
• Data Converters: A/D 4x8b
• Oscillator Type: Internal
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 8-CDIP (0.300", 7.62mm) Window
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Connectivity: -

FIGURE 3-2:
EXAMPLE 3-1:
PIC12C67X
3.1
The clock input (from OSC1) is internally divided by
four to generate four non-overlapping quadrature
clocks, namely Q1, Q2, Q3 and Q4. Internally, the pro-
gram counter (PC) is incremented every Q1, and the
instruction is fetched from the program memory and
latched into the instruction register in Q4. The instruc-
tion is decoded and executed during the following Q1
through Q4. The clocks and instruction execution flow
is shown in Figure 3-2.
DS30561B-page 10
1. MOVLW 55h
2. MOVWF GPIO
3. CALL
4. BSF
5. Instruction @ address SUB_1
All instructions are single cycle, except for any program branches. These take two cycles since the fetched
instruction is “flushed” from the pipeline while the new instruction is being fetched and then executed.
Clocking Scheme/Instruction Cycle
OSC2/CLKOUT
INTRC modes)
(EXTRC and
SUB_1
GPIO, BIT3 (Forced NOP)
OSC1
CLOCK/INSTRUCTION CYCLE
PC
Q1
Q2
Q3
Q4
INSTRUCTION PIPELINE FLOW
Q1
Execute INST (PC-1)
Fetch 1
Fetch INST (PC)
T
Q2
CY
0
PC
Q3
Execute 1
Fetch 2
T
CY
Q4
1
Q1
Execute 2
Fetch 3
T
Execute INST (PC)
CY
Fetch INST (PC+1)
Q2
2
PC+1
3.2
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
(i.e., GOTO), then two cycles are required to complete
the instruction (Example 3-1).
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).
Q3
Execute 3
Fetch 4
T
CY
Instruction Flow/Pipelining
Q4
3
Q1
Fetch SUB_1
Execute INST (PC+1)
Flush
T
Fetch INST (PC+2)
CY
Q2
1999 Microchip Technology Inc.
4
PC+2
Q3
Execute SUB_1
Q4
T
CY
5
Internal
phase
clock