I notice from the Zilog datasheet on the Z80 that with the I/O (IN and OUT) group of instructions, the contents of various registers are often placed in the top 8 bits of the address bus (depending...

I am recently browsing GPIO driver for pi2, I found user space pi2 GPIO lib (like RPi.GPIO 0.5.11 of python) use /dev/mem for BCM2708 (begins at 0x20000000,and GPIO begins at 0x200000 relatively) t...

I am reading some code of Linux. The keyboard.S has something like outb %al,$0x61 and inb $0x61,%al I think the pending 'b' means 'byte', but i still cannot find what these instructions mean....