Controller port registers

NES

Addr	7654.3210	Function
$4016 (W)	----.---A	Output data (strobe) to both controllers.
	----.-CBA	Output data to the expansion port.
$4016 (R)	---4.3--0	Read data from controller port #1.
	---4.3210	Read data from expansion port.
$4017 (R)	---4.3--0	Read data from controller port #2.
	---4.3210	Read data from expansion port.

Famicom

Addr	7654.3210	Function
$4016 (W)	----.---A	Output strobe to both controllers.
	----.-CBA	Output data to the expansion port.
$4016 (R)	----.-M-0	Read data from controller #1 and microphone state from controller #2
	----.--1-	Read data from expansion port.
$4017 (R)	----.---0	Read data from controller #2.
	---4.3210	Read data from expansion port.