[avr-gcc-list] Problem with interrupts/vector table with ATmega16

[Pat Deegan]

Hello,

I've been experiencing trouble whilst trying to enable interrupts.  The
code works fine but when I add the call to sei() nothing works.  I
thought I figured out that the program was reseting because it was
calling an unassigned interrupt handler (thus, jumping to
__bad_interrupt and resetting).  So I added a bunch of EMPTY_INTERRUPT()
signal handlers... no go.

Since that didn't work, I took a peek at the disassembled code,
specifically the vector init (included below).

I am building for the atmega16, compiling with:

avr-gcc -I. -I../include/ -g -mmcu=atmega16 -Os -fpack-struct \
 -fshort-enums -funsigned-bitfields -funsigned-char -Wall \
 -Wstrict-prototypes -Wa,-ahlms=file.lst \
 file.c -o file.o

and linking with:

avr-gcc -Wl,-Map,midiparse.out.map -mmcu=atmega16 -lm  -o prog.out \
 file1.o file2.o file3.o


The vector init is (I've added comments to indicate where each line
jumps to):


00000000 <__vectors>:
       0:       0c 94 0f 01     jmp     0x21e  ; reset, goes to __init
       4:       0c 94 c5 0d     jmp     0x1b8a ; jmp to SIG_INTERRUPT0
       8:       0c 94 23 0e     jmp     0x1c46 ; this goes to
SIG_INTERRUPT1
       c:       0c 94 4c 01     jmp     0x298  ; jmp to
SIG_OUTPUT_COMPARE2
      10:       0c 94 b1 02     jmp     0x562  ; this points to
SIG_OVERFLOW2
      14:       0c 94 2a 01     jmp     0x254  ; __bad_interrupt
      18:       0c 94 49 01     jmp     0x292  ; SIG_OUTPUT_COMPARE1A
      1c:       0c 94 4a 01     jmp     0x294  ; SIG_OUTPUT_COMPARE1B
      20:       0c 94 9b 0f     jmp     0x1f36 ; SIG_OVERFLOW1 handler
      24:       0c 94 2f 08     jmp     0x105e ; this jmps to
SIG_OVERFLOW0
      28:       0c 94 45 01     jmp     0x28a  ; SIG_SPI
      2c:       0c 94 2a 01     jmp     0x254 ; __bad_interrupt
      30:       0c 94 2a 01     jmp     0x254 ; __bad_interrupt
      34:       0c 94 2a 01     jmp     0x254 ; __bad_interrupt
      38:       0c 94 50 01     jmp     0x2a0 ; SIG_ADC
      3c:       0c 94 2a 01     jmp     0x254 ; __bad_interrupt
      40:       0c 94 51 01     jmp     0x2a2 ; SIG_COMPARATOR
      44:       0c 94 4f 01     jmp     0x29e ; SIG_2WIRE_SERIAL
      48:       0c 94 47 01     jmp     0x28e ; SIG_INTERRUPT2
      4c:       0c 94 48 01     jmp     0x290 ; SIG_OUTPUT_COMPARE0
      50:       0c 94 46 01     jmp     0x28c ; SIG_SPM_READY


                                                                                
                                             and it doesn't seem right.  None 
of the vectors are pointing to any of the SIG_UART* handlers (some of which are 
declared as EMPTY_INTERRUPT()s) and others look like they're in the wrong spot 
(though the order looks ok). 

The ATmega16 specs have an interrupt table that says:

Vector No. Program Address(2) Source Interrupt Definition

1       $000(1) RESET External Pin, Power-on Reset, Brown-out Reset, Watchdog
Reset, and JTAG AVR Reset 
2       $002 INT0 External Interrupt Request 0 
3       $004 INT1 External Interrupt Request 1 
4       $006 TIMER2 COMP Timer/Counter2 Compare Match 
5       $008 TIMER2 OVF Timer/Counter2 Overflow 
6       $00A TIMER1 CAPT Timer/Counter1 Capture Event 
7       $00C TIMER1 COMPA Timer/Counter1 Compare Match A 
8       $00E TIMER1 COMPB Timer/Counter1 Compare Match B 
9       $010 TIMER1 OVF Timer/Counter1 Overflow 
10      $012 TIMER0 OVF Timer/Counter0 Overflow 
11      $014 SPI, STC Serial Transfer Complete 
12      $016 USART, RXC USART, Rx Complete 
13      $018 USART, UDRE USART Data Register Empty 
14      $01A USART, TXC USART, Tx Complete 
15      $01C ADC ADC Conversion Complete 
16      $01E EE_RDY EEPROM Ready 
17      $020 ANA_COMP Analog Comparator 
18      $022 TWI Two-wire Serial Interface 
19      $024 INT2 External Interrupt Request 2 
20      $026 TIMER0 COMP Timer/Counter0 Compare Match 
21      $028 SPM_RDY Store Program Memory Ready

Am I reading this wrong or don't these match the disassembled code? 
First, it looks like the AVR expects a list of addresses 2 bytes wide
while the actual jmps take 4 bytes, which gradually shifts everything
more and more out of sync.  Or is it that Atmel is refering to the
address of 16 bit words?

In any case, any idea why the UART sig handlers aren't showing up in the
vector table?

TIA.

Regards,
-- 
Pat Deegan
http://www.psychogenic.com/
PGP Key: http://www.keyserver.net 0x03F86A50