PIC16C62B/72A
APPENDIX C: MIGRATION FROM
BASE-LINE TO
MID-RANGE DEVICES
This section discusses how to migrate from a baseline
device (i.e., PIC16C5X) to a mid-range device (i.e.,
PIC16CXXX).
The following are the list of modifications over the
PIC16C5X microcontroller family:
1.
Instruction word length is increased to 14-bits.
This allows larger page sizes both in program
memory (2K now as opposed to 512 before) and
register file (128 bytes now versus 32 bytes
before).
2. A PC high latch register (PCLATH) is added to
handle program memory paging. Bits PA2, PA1,
PA0 are removed from STATUS register.
3. Data memory paging is redefined slightly.
STATUS register is modified.
4. Four new instructions have been added:
RETURN, RETFIE, ADDLW,
and
SUBLW.
Two instructions
TRIS
and
OPTION
are being
phased out although they are kept for compati-
bility with PIC16C5X.
5. OPTION_REG and TRIS registers are made
addressable.
6. Interrupt capability is added. Interrupt vector is
at 0004h.
7. Stack size is increased to 8 deep.
8. Reset vector is changed to 0000h.
9. Reset of all registers is revisited. Five different
reset (and wake-up) types are recognized. Reg-
isters are reset differently.
10. Wake up from SLEEP through interrupt is
added.
11. Two separate timers, Oscillator Start-up Timer
(OST) and Power-up Timer (PWRT) are
included for more reliable power-up. These tim-
ers are invoked selectively to avoid unnecessary
delays on power-up and wake-up.
12. PORTB has weak pull-ups and interrupt on
change feature.
13. T0CKI pin is also a port pin (RA4) now.
14. FSR is made a full eight bit register.
15. “In-circuit serial programming” is made possible.
The user can program PIC16CXX devices using
only five pins: V
DD
, V
SS
, MCLR/V
PP
, RB6 (clock)
and RB7 (data in/out).
16. PCON status register is added with a Power-on
Reset status bit (POR).
17. Code protection scheme is enhanced such that
portions of the program memory can be pro-
tected, while the remainder is unprotected.
18. Brown-out protection circuitry has been added.
Controlled by configuration word bit BODEN.
Brown-out reset ensures the device is placed in
a reset condition if V
DD
dips below a fixed set-
point.
To convert code written for PIC16C5X to PIC16CXXX,
the user should take the following steps:
1.
2.
Remove any program memory page select
operations (PA2, PA1, PA0 bits) for
CALL, GOTO.
Revisit any computed jump operations (write to
PC or add to PC, etc.) to make sure page bits
are set properly under the new scheme.
Eliminate any data memory page switching.
Redefine data variables to reallocate them.
Verify all writes to STATUS, OPTION, and FSR
registers since these have changed.
Change reset vector to 0000h.
3.
4.
5.
DS35008B-page 112
Preliminary
©
1999 Microchip Technology Inc.
MICROCHIP [ MICROCHIP TECHNOLOGY ]
