I'm having trouble getting a TMR2 interrupt.The code below
outputs a 240Hz / 50% PWM from Portb.3  The intention is
to use the TMR2 IRQ as a signal to read external pots (via a
4051 and TLC549) that are adjusted to modify the frequency
/ duty cycle. A match is occuring between TMR2 and PR2 as
the PWM maintains itself. I've used Timer0 as an alternate
source and the ISR does get entered as expected

The concept is fairly similar to Olin's HAL project, in that during
the ISR a new value may be loaded into CCPR1L. However, as
Olin's writing style is quite different to mine I may have missed
something with the IRQ set-up. Microchip seem not to have any
examples of TMR2 IRQ code (they poll TMR2IF), so I'm looking
for help

TIA

===================================================

         list p=16F628
         #include <p16F628.inc>

led equ 0x07

       __config _intrc_osc_noclkout & _wdt_off & _pwrte_on & _lvp_off &
_boden_off

         org 0x00
         goto entry

         org 0x04
         goto irq

entry    clrf   porta
         movlw  0x07
         movwf  cmcon
         clrf   status        ;set rp0, rp1 = 0 = Bank0

         bsf    status,rp0    ;tris registers in bank1
         bcf    status,rp1

         movlw  b'00000000'   ;oooo oooo , Porta all o/p
         movwf  trisa

         movlw  b'00100000'   ;ooio oooo all o/p except Serial Data
         movwf  trisb

         movlw  0x86                ;TMR0 pre-scaler= 128 =30Hz IRQ
         movwf  option_reg

         bcf    status,rp0
         bcf    status,rp1

         clrf   porta           ;4051 A = B = C = 0
         clrf   ashad         ;clear shadow

         movlw  b'01010000'   ;TLC549 Clock high, CS high
         movwf  portb
         clrf   fsr

         clrf   ccp1con       ;CCP Module off, set up PWM
         clrf   tmr2
         movlw  b'11111100'   ;TMR2 - PR2 match value
         movwf  pr2
         movlw  b'01111111'   ;duty cycle MSBs
         movwf  ccpr1l
         clrf   intcon
         bsf    status,rp0
         clrf   pie1
         bcf    status,rp0
         clrf   pir1
         movlw  b'00011100'   ;DC LSBs <5:4>, 11xx = PWM mode
         movwf  ccp1con
         bcf    t2con,t2ckps0 ;PS 00 1: 1
                                           ;       01 1:4  selected
         bsf    t2con,t2ckps1 ;       1x 1:16
         nop
         bsf    t2con,tmr2on  ;Timer2 enabled

         bsf    intcon,peie       ;enable peripheral IRQs
         bsf    pie1,tmr2ie      ;enable TMR2 IRQs
         bcf    pir1,tmr2if        ;reset TMR2 IRQ flag

;         bsf    intcon,t0ie
          bsf    intcon,gie        ;enable IRQs

loop     goto   loop

;=============================
;        ISR
;=============================

irq      bcf    pir1,tmr2if        ;reset IRQ source flags
         bcf    intcon,t0if

         bsf    portb,led            ;ISR activity indicator
         nop
         bcf    portb,led

         retfie                            ;temporary return

         movwf  wtemp
         swapf  status,w
         movwf  stemp

         call   readadc              ;get pot value

         movf   dbuff,w
         movwf  ccpr1l              ;into PWM DC register

         swapf  stemp,w
         movwf  status
         swapf  wtemp,f
         swapf  wtemp,w
         retfie

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