Elapsed timer not working as expected at 64MHz

[Demon]

OSC 64 (16 + PLL)

PS:00000000 00000100 <--- Dec=4
TC:01100011 11001000 <--- Dec=25544

I had same results manually this afternoon.

Robert

[richard]

ok next whats in T1CON ?

[Demon]

Looking at the datasheet for 18F44K22, timer 1 has a 2 bit prescaler.

4 (100) takes 3 bits.

Gonna try timer 2.

...
13.0 TIMER2/4/6 MODULE p.175
...
• 8-bit Timer and Period registers (TMRx and PRx,
respectively)
• Readable and writable (both registers)
• Software programmable prescaler (1:1, 1:4, 1:16)
• Software programmable postscaler (1:1 to 1:16)
...

EDIT: Darn, DT Elapsed include only has Timer1...

Robert

[Demon]

Was looking at T1CON register and noticed this:

TxCKPS<1:0>: Timer1/3/5 Input Clock Prescale Select bits
11 = 1:8 Prescale value
10 = 1:4 Prescale value
01 = 1:2 Prescale value
00 = 1:1 Prescale value

So that is 2 bits.

bit 7-6 TMRxCS<1:0>: Timer1/3/5 Clock Source Select bits
  11 =Reserved. Do not use.
  10 =Timer1/3/5 clock source is pin or oscillator:
    If TxSOSCEN = 0:
      External clock from TxCKI pin (on the rising edge)
    If TxSOSCEN = 1:
      Crystal oscillator on SOSCI/SOSCO pins
  01 =Timer1/3/5 clock source is system clock (FOSC)
  00 =Timer1/3/5 clock source is instruction clock (FOSC/4)

bit 5-4 TxCKPS<1:0>: Timer1/3/5 Input Clock Prescale Select bits
  11 = 1:8 Prescale value
  10 = 1:4 Prescale value
  01 = 1:2 Prescale value
  00 = 1:1 Prescale value

bit 3 TxSOSCEN: Secondary Oscillator Enable Control bit
  1 = Dedicated Secondary oscillator circuit enabled
  0 = Dedicated Secondary oscillator circuit disabled

bit 2 TxSYNC: Timer1/3/5 External Clock Input Synchronization Control bit
    TMRxCS<1:0> = 1X
  1 = Do not synchronize external clock input
  0 = Synchronize external clock input with system clock (FOSC)
    TMRxCS<1:0> = 0X
  This bit is ignored. Timer1/3/5 uses the internal clock when TMRxCS<1:0> = 1X.

bit 1 TxRD16: 16-Bit Read/Write Mode Enable bit
  1 = Enables register read/write of Timer1/3/5 in one 16-bit operation
  0 = Enables register read/write of Timer1/3/5 in two 8-bit operation

bit 0 TMRxON: Timer1/3/5 On bit
  1 = Enables Timer1/3/5
  0 = Stops Timer1/3/5
    Clears Timer1/3/5 Gate flip-flop

T1CON=00000000

Robert

[richard]

ITS NOT using the prescaler those bits need to be 00 ie 1:1
@64mhz with a preload of 25544 you get a tmr1 int every 2.5mS dt's int routine inc's the tips counter till its 4 then inc's the elapsed time clock I count ie once every 10mS

next step after confirming t1con is ok is to toggle a pin in the int routine as per what Sheldon suggested and verify 2.5mS ints are occurring

[Demon]

In the Elapsed include:

...
' -------------- calc timer reload Constants -------------------------------
ASM
T1PS = 1                             ; start with 1:1 postscaler
TimerConst = ((OSC*1000000)/4/100)   ; how many timer ticks will it take
  while TimerConst > 65400           ; if it's more than the timer can count
T1PS = T1PS * 2                      ;   double the postscaler
TimerConst = TimerConst / 2          ;   halve the count
  endw
TimerConst = 65536 - TimerConst + 8  ; final reload value
...

Darryl talks about a post-scaler. Timers 1, 3 and 5 have none for a 18F44K22?

Neither does Timer 0, only Timers 2,4 and 6 have pre and post-scalers.

Robert

[richard]

Darryl talks about a post-scaler. Timers 1, 3 and 5 have none for a 18F44K22?

Neither does Timer 0, only Timers 2,4 and 6 have pre and post-scalers

hence the T1PS VAR

[richard]

t1con looks good should be 0 or 1 (on or off) depending on what the int routine is up to