PIC16HV785 Microchip Technology Inc., PIC16HV785 Datasheet - Page 122

• Manufacturer Part Number: PIC16HV785
• Description: 20-pin Flash-based 8-bit Cmos Microcontroller
• Manufacturer: Microchip Technology Inc.

PIC16F785/HV785
15.4
During an interrupt, only the return PC value is saved
on the stack. Typically, users may wish to save key
registers during an interrupt (e.g., W and STATUS
registers). This must be implemented in software.
Since the last 16 bytes of all banks are common in the
PIC16F785/HV785 (see Figure 2-2), temporary hold-
ing registers W_TEMP and STATUS_TEMP should be
placed in here. These 16 locations do not require
banking, therefore, making it easier to save and restore
context. The same code shown in Example 15-1 can
be used to:
• Store the W register
• Store the STATUS register
• Execute the ISR code
• Restore the Status (and Bank Select Bit register)
• Restore the W register
EXAMPLE 15-1:
DS41249D-page 120
Note:
MOVWF
SWAPF
CLRF
MOVWF
:
:(ISR)
:
SWAPF
MOVWF
SWAPF
SWAPF
Context Saving During Interrupts
The PIC16F785/HV785 normally does not
require saving the PCLATH. However, if
computed GOTO’s are used in the ISR and
the main code, the PCLATH must be
saved and restored in the ISR.
W_TEMP
STATUS,W
STATUS
STATUS_TEMP
STATUS_TEMP,W
STATUS
W_TEMP,F
W_TEMP,W
SAVING STATUS AND W REGISTERS IN RAM
;Copy W to TEMP register
;Swap status to be saved into W (swap does not affect status)
;bank 0, regardless of current bank, Clears IRP,RP1,RP0
;Save status to bank zero STATUS_TEMP register
;Insert user code here
;Swap STATUS_TEMP register into W
;(sets bank to original state)
;Move W into Status register
;Swap W_TEMP
;Swap W_TEMP into W
Preliminary
© 2006 Microchip Technology Inc.