PIC12F635-I/SN Microchip Technology, PIC12F635-I/SN Datasheet - Page 34

• Manufacturer Part Number: PIC12F635-I/SN
• Description: IC MCU FLASH 1KX14 8SOIC
• Manufacturer: Microchip Technology
• Series: PIC® 12Fr

Specifications of PIC12F635-I/SN

• Program Memory Type: FLASH
• Program Memory Size: 1.75KB (1K x 14)
• Package / Case: 8-SOIC (3.9mm Width)
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Peripherals: Brown-out Detect/Reset, POR, WDT
• Number Of I /o: 5
• Eeprom Size: 128 x 8
• Ram Size: 64 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Processor Series: PIC12F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 64 B
• Interface Type: RS- 232/SPI/USB
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 6
• Number Of Timers: 2
• Operating Supply Voltage: 2 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: PG164130, DV164035, DV244005, DV164005, PG164120, ICE2000, DV164120, DM163029, DV164101, DM163014
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AC162057 - MPLAB ICD 2 HEADER 14DIP
• Data Converters: -
• Connectivity: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

during a CALL or GOTO instruction (PCLATH<4:3>
PIC12F635/PIC16F636/639
2.3
The Program Counter (PC) is 13 bits wide. The low byte
comes from the PCL register, which is a readable and
writable register. The high byte (PC<12:8>) is not
directly readable or writable and comes from PCLATH.
On any Reset, the PC is cleared. Figure 2-5 shows the
two situations for the loading of the PC. The upper
example in Figure 2-5 shows how the PC is loaded on a
write to PCL (PCLATH<4:0>
example in Figure 2-5 shows how the PC is loaded
PCH).
FIGURE 2-5:
2.3.1
Executing any instruction with the PCL register as the
destination
Counter PC<12:8> bits (PCH) to be replaced by the
contents of the PCLATH register. This allows the entire
contents of the program counter to be changed by
writing the desired upper 5 bits to the PCLATH register.
When the lower 8 bits are written to the PCL register, all
13 bits of the program counter will change to the values
contained in the PCLATH register and those being
written to the PCL register.
A computed GOTO is accomplished by adding an offset
to the program counter (ADDWF PCL). Care should be
exercised when jumping into a look-up table or
program branch table (computed GOTO) by modifying
the PCL register. Assuming that PCLATH is set to the
table start address, if the table length is greater than
255 instructions or if the lower 8 bits of the memory
address rolls over from 0xFF to 0x00 in the middle of
the table, then PCLATH must be incremented for each
address rollover that occurs between the table
beginning and the target location within the table.
For more information refer to Application Note AN556,
“Implementing a Table Read” (DS00556).
DS41232D-page 32
PC
PC
12
12 11 10
2
PCL and PCLATH
5
PCH
PCLATH<4:3>
PCH
MODIFYING PCL
simultaneously causes the
PCLATH
PCLATH<4:0>
8
PCLATH
8
7
7
LOADING OF PC IN
DIFFERENT SITUATIONS
PCL
PCL
11
8
PCH). The lower
0
0
Instruction with
Opcode<10:0>
ALU Result
GOTO, CALL
Destination
Program
PCL as
2.3.2
The
8-level x 13-bit wide hardware stack (see Figure 2-1).
The stack space is not part of either program or data
space and the Stack Pointer is not readable or writable.
The PC is PUSHed onto the stack when a CALL
instruction is executed or an interrupt causes a branch.
The stack is POPed in the event of a RETURN, RETLW
or a RETFIE instruction execution. PCLATH is not
affected by a PUSH or POP operation.
The stack operates as a circular buffer. This means that
after the stack has been PUSHed eight times, the ninth
push overwrites the value that was stored from the first
push. The tenth push overwrites the second push (and
so on).
2.4
The INDF register is not a physical register. Addressing
the INDF register will cause indirect addressing.
Indirect addressing is possible by using the INDF
register. Any instruction using the INDF register
actually accesses data pointed to by the File Select
Register (FSR). Reading INDF itself indirectly will
produce 00h. Writing to the INDF register indirectly
results in a no operation (although Status bits may be
affected). An effective 9-bit address is obtained by
concatenating the 8-bit FSR and the IRP bit of the
STATUS register, as shown in Figure 2-6.
A simple program to clear RAM location 20h-2Fh using
indirect addressing is shown in Example 2-1.
EXAMPLE 2-1:
NEXT
CONTINUE
Note 1: There are no Status bits to indicate stack
PIC12F635/PIC16F636/639
2: There are no instructions/mnemonics
Indirect Addressing, INDF and
FSR Registers
STACK
MOVLW
MOVWF
CLRF
INCF
BTFSS
GOTO
overflow or stack underflow conditions.
called PUSH or POP. These are actions
that occur from the execution of the CALL,
RETURN, RETLW and RETFIE instructions
or the vectoring to an interrupt address.
0x20
FSR
INDF
FSR
FSR,4
NEXT
INDIRECT ADDRESSING
© 2007 Microchip Technology Inc.
;initialize pointer
;to RAM
;clear INDF register
;INC POINTER
;all done?
;no clear next
;yes continue
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