Games Port, Keyboard and Mouse - Computer Busses - page 191

PARE Parity bit - 1 = last byte has a parity error, 0 = no error.

TIM General time-out - 1 = error, 0 = no error.

AUXB Output buffer for auxiliary device - 1 = holds data for auxiliary device,

0 = holds keyboard data.

KEYL Keyboard lock status - 1 = keyboard unlocked, 0 = keyboard locked.

C/D Command/data - 1 command byte written via port 64h, data byte writ-

ten via port 60h.

SYSF. System flag - 1 = self-test successful, 0 = power-on reset.

INPB. Input buffer status - 0 = Data in input buffer, 0 = no data.

OUTB. Output buffer status - 0 = Controller data in output buffer, 0 = buffer

empty.

The auxiliary device is typically a PS/2 style mouse. Program 10.2 shows an example pro-
gram which reads from the keyboard buffer. It disables the IRQ1 interrupt. (Note that this
may cause some systems to not respond to the keyboard if the program does not terminate
properly.)

Address: 64h
Status register

PARE TIM AUXB KEYL C/D SYSF INPB OUTB

Figure 10.7 Status register bits

Table 10.2 Control register commands

Code Command Return value (in output buffer)

a7h Disable auxiliary device

a8h Enable auxiliary device

a9h Check interface to auxiliary device 00h = no error, 01h = clock line low, 02h = clock

line high, 03h = data line low, 04h = data line
high and ffh = no auxiliary device.

aah Self-test 55h, on success

abh Check keyboard interface 00h = no error, 01h = clock line low, 02h = clock

line high, 03h = data line low, 04h = data line
high and ffh = no auxiliary device

adh Disable keyboard

aeh Enable keyboard

c0h Read input port

c1h Read input port (low)

c2h Read input port (high)

d0h Read output port

d1h Write output port

d2h Write keyboard output buffer

d3h Write output buffer of auxiliary device

d4h Write auxiliary device

e0h Read test input port