PIC16F628-04/SS Microchip Technology, PIC16F628-04/SS Datasheet - Page 27

• Manufacturer Part Number: PIC16F628-04/SS
• Description: IC MCU FLASH 2KX14 COMP 20SSOP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F628-04/SS

• Core Size: 8-Bit
• Program Memory Size: 3.5KB (2K x 14)
• Core Processor: PIC
• Speed: 4MHz
• Connectivity: UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 16
• Program Memory Type: FLASH
• Eeprom Size: 128 x 8
• Ram Size: 224 x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 20-SSOP
• Controller Family/series: PIC16F
• No. Of I/o's: 16
• Eeprom Memory Size: 128Byte
• Ram Memory Size: 224Byte
• Cpu Speed: 4MHz
• No. Of Timers: 3
• Package: 20SSOP
• Device Core: PIC
• Family Name: PIC16
• Maximum Speed: 4 MHz
• Operating Supply Voltage: 3.3|5 V
• Data Bus Width: 8 Bit
• Number Of Programmable I/os: 16
• Interface Type: SCI/USART
• Number Of Timers: 3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: XLT20SS-1 - SOCKET TRANSITION 18DIP 20SSOPAC164307 - MODULE SKT FOR PM3 28SSOPAC164018 - MODULE SKT PROMATEII 20SSOP
• Data Converters: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

3.3
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 3-3 shows
the two situations for the loading of the PC. The upper
example in the figure shows how the PC is loaded on a
write to PCL (PCLATH<4:0> → PCH). The lower exam-
ple in the figure shows how the PC is loaded during a
CALL or GOTO instruction (PCLATH<4:3> → PCH).
FIGURE 3-3:
3.3.1
A computed GOTO is accomplished by adding an offset
to the program counter (ADDWF PCL). When doing a
table read using a computed GOTO method, care
should be exercised if the table location crosses a PCL
memory boundary (each 256 byte block). Refer to the
application note “Implementing a Table Read” (AN556).
3.3.2
The PIC16F62X family has an 8-level deep x 13-bit
wide hardware stack (Figure 3-1 and Figure 3-2). 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,
RETFIE instruction execution. PCLATH is not affected
by a PUSH or POP operation.
 2003 Microchip Technology Inc.
PC
PC
12
12
2
PCL and PCLATH
11 10
5
PCH
PCLATH<4:3>
PCH
COMPUTED GOTO
STACK
PCLATH
PCLATH<4:0>
8
PCLATH
8
7
7
LOADING OF PC IN
DIFFERENT SITUATIONS
PCL
PCL
11
8
0
0
Instruction with
PCL as
Destination
ALU result
GOTO, CALL
Opcode <10:0>
RETLW or a
Preliminary
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).
3.4
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 actu-
ally 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 register and the IRP bit (STATUS<7>), as
shown in Figure 3-4.
A simple program to clear RAM location 20h-2Fh using
indirect addressing is shown in Example 3-1.
EXAMPLE 3-1:
NEXT
Note 1: There are no STATUS bits to indicate
Indirect Addressing, INDF and
FSR Registers
2: There are no instructions/mnemonics
movlw
movwf
clrf
incf
btfss
goto
stack
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.
overflow
0x20
FSR
INDF
FSR
FSR,4
NEXT
Indirect Addressing
PIC16F62X
;initialize pointer
;to RAM
;clear INDF register
;inc pointer
;all done?
;no clear next
;yes continue
or
stack
DS40300C-page 25
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