Bizarre interaction between T1MR0 INTs and UART0's Baudrate
2004-02-01 by microbit
This is a weird one, I've reduced the functions to the ones that seem
to
interfere with one another :
(on LPC2106, clocked at 10 MHz, on Nohau tester board)
I initialise T1 to Reset and Interrupt on Match(0) every 1 mS.
(T1PR=2, T1MR0=5000, T1MCR=3)
Works 100% alone or mixed with other functions.
I initialise UART0 to run at 19200 Bps RX and TX Interrupts.
(Or even polled with just a single char TXd, no INTs).
Works 100% alone or mixed with other functions.
When running T1MR0 Interrupt **AND** UART0 at 19,200 Bps
things go ape :
-------------------------------------------------------------------------------------------
- After Cold reset, T1MR0 Interrupt now ticks 6 TIMES SLOWER,
and the Baud rate is correct providing I have P0.15 and P0.14
jumpers
to LEDS in place.
(If P0.14 and P0.15 are floating - no jumpers - then the
Timer is correct but
;baudrate is too fast)
- If the same program is executed from RAM, and it is started with the
P0.14
and P0.15 jumpers installed, the Timer Interrupt now ticks
correctly but my Baudrate
is suddenly 6 times faster (1 bit time for 19,200 is only
17.06687 uS)
????
VPBDIV is left at its default so pclk = cclk/4.
I've changed around slots on the VIC, swapped priorities between the 2 but
it's not there.
The same syndrome occurs when the UART INTs are disabled, and I just TX
0x55 continuously
with polling on U0LSR.
Has anyone seen anything like this ???
B regards,
Kris