GPIO
GPIO (General Purpose Input/Output)
How does tagging bit 28 of address 0x2009 C020 turn the LED on and off in the lab for ECE 222?
Info
Peripherals (I/O devices and timers) have interface registers mapped to addresses not used by Memory#memory
Example
Lab microcontrollers:
GPIO port 1 connects to 32 I/O Pins, and pins 28, 29, and 31 are connected to LEDs.
Port 1 has registers at addresses:
0x2009 C020(FIODIR, fast input/output directory)0x2009 C030(FIOMASK)0x2009 C034(FIOPIN)0x2009 C038(FIOSET)0x2009 C03C(FIOCLR)
To toggle bit 28 of GPIO port 1:
MOV32 R0, #0x2009C020 ; LDR R0, #0x2009C020
LDR R1, [R0]
EOR R1, #1 << 28 ; Toggle 28th bit
STR R1, [R0]