I hate to say this, after the messy events of the past couple of days [see this thread for the gory details],
but there are errors in that file for the Mega board, just as on the Mega board schematic and pinout diagrams. Basically the Arduino "experts" don't seem to see the problems - or else they might actually [u]fix[/u] them - but dumb coders like me get burned, and end up wasting an awful lot of time.
First off, on the spreadsheet where it says
pin Int 8, Pin Int 4, etc
they are referring to PCINT8, PCINT4, ie the pin change interrupts. No big deal.
However, the other lines are where the big mess is, namely
pin Arduino 328 Arduino Mega
2 PD 2 Ext Int 0 PE 4 PWM T3B, INT4
3 PD 3 PWM T2B, Ext Int 1 PE 5 PWM T3C, INT5
18 PC 4 4 I2C SDA PD 3 USART1 TX, Ext Int 3
19 PC 5 5 I2C SCL PD 2 USART1 RX, Ext Int 2
20 PD 1 I2C SDA, Ext Int 1
21 PD 0 I2C SCL, Ext Int 0
So, without going through the entire other thread again, what you need to do is look at the following web page
to get the "correct" info, where it says,
The table below shows the available interrupt pins on various boards.
Board int.0 int.1 int.2 int.3 int.4 int.5
Uno 2 3
Mega2560 2 3 21 20 19 18
You'll notice these pages match for the UNO board, but not for the Mega.
So, hopefully this will save Marcello some time when he tries to use these things.