PIC16F84A-20/SO Microchip Technology, PIC16F84A-20/SO Datasheet - Page 32

• Manufacturer Part Number: PIC16F84A-20/SO
• Description: IC MCU FLASH 1KX14 EE 18SOIC
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F84A-20/SO

• Core Size: 8-Bit
• Program Memory Size: 1.75KB (1K x 14)
• Core Processor: PIC
• Speed: 20MHz
• Peripherals: POR, WDT
• Number Of I /o: 13
• Program Memory Type: FLASH
• Eeprom Size: 64 x 8
• Ram Size: 68 x 8
• Voltage - Supply (vcc/vdd): 4 V ~ 5.5 V
• Oscillator Type: External
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 18-SOIC (7.5mm Width)
• Controller Family/series: PIC16F
• No. Of I/o's: 13
• Eeprom Memory Size: 64Byte
• Ram Memory Size: 68Byte
• Cpu Speed: 20MHz
• No. Of Timers: 1
• Processor Series: PIC16F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 68 B
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 13
• Number Of Timers: 8
• Operating Supply Voltage: 2 V to 5.5 V
• Maximum Operating Temperature: + 70 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: ICE2000
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: XLT18SO-1 - SOCKET TRANSITION 18SOIC 300MILI3-DB16F84A - BOARD DAUGHTER ICEPIC3309-1075 - ADAPTER 18-SOIC TO 18-SOIC309-1011 - ADAPTER 18-SOIC TO 18-DIP309-1010 - ADAPTER 18-SOIC TO 18-DIPAC164010 - MODULE SKT PROMATEII DIP/SOIC
• Data Converters: -
• Connectivity: -
• Lead Free Status / Rohs Status: Details

PIC16F84A
6.9
During an interrupt, only the return PC value is saved
on the stack. Typically, users wish to save key register
values during an interrupt (e.g., W register and
STATUS register). This is implemented in software.
The code in Example 6-1 stores and restores the
STATUS and W register’s values. The user defined
registers, W_TEMP and STATUS_TEMP are the tem-
porary storage locations for the W and STATUS
registers values.
EXAMPLE 6-1:
6.10
The Watchdog Timer is a free running On-Chip RC
Oscillator which does not require any external
components. This RC oscillator is separate from the
RC oscillator of the OSC1/CLKIN pin. That means that
the WDT will run even if the clock on the OSC1/CLKIN
and OSC2/CLKOUT pins of the device has been
stopped, for example, by execution of a SLEEP
instruction. During normal operation, a WDT time-out
generates a device RESET. If the device is in SLEEP
mode, a WDT wake-up causes the device to wake-up
and continue with normal operation. The WDT can be
permanently disabled by programming configuration bit
WDTE as a '0' (Section 6.1).
DS35007B-page 30
PUSH
ISR
POP
Context Saving During Interrupts
Watchdog Timer (WDT)
MOVWF
SWAPF
MOVWF
:
:
:
:
SWAPF
MOVWF
SWAPF
SWAPF
W_TEMP
STATUS,
STATUS_TEMP
STATUS_TEMP,W
STATUS
W_TEMP,
W_TEMP,
SAVING STATUS AND W REGISTERS IN RAM
W
F
W
; Copy W to TEMP register,
; Swap status to be saved into W
; Save status to STATUS_TEMP register
:
; Interrupt Service Routine
; should configure Bank as required
;
; Swap nibbles in STATUS_TEMP register
; and place result into W
; Move W into STATUS register
; (sets bank to original state)
; Swap nibbles in W_TEMP and place result in W_TEMP
; Swap nibbles in W_TEMP and place result into W
Example 6-1 does the following:
a)
b)
c)
d)
e)
6.10.1
The WDT has a nominal time-out period of 18 ms, (with
no prescaler). The time-out periods vary with
temperature, V
part (see DC specs). If longer time-out periods are
desired, a prescaler with a division ratio of up to 1:128
can be assigned to the WDT under software control by
writing to the OPTION_REG register. Thus, time-out
periods up to 2.3 seconds can be realized.
The CLRWDT and SLEEP instructions clear the WDT
and the postscaler (if assigned to the WDT) and pre-
vent it from timing out and generating a device
RESET condition.
The TO bit in the STATUS register will be cleared upon
a WDT time-out.
Stores the W register.
Stores the STATUS register in STATUS_TEMP.
Executes the Interrupt Service Routine code.
Restores the STATUS (and bank select bit)
register.
Restores the W register.
WDT PERIOD
DD
and process variations from part to
2001 Microchip Technology Inc.