HP dx7300 CPU Commands to the, Table 5-15. (Continued)

Input/Output Interfaces

	Table 5-15. (Continued)
	CPU Commands to the 8042
Value	Command Description
A9h	Test the clock and data lines of the pointing device interface and place test results in the output
	buffer.
	00h = No error detected
	01h = Clock line stuck low
	02h = Clock line stuck high
	03h = Data line stuck low
	04h = Data line stuck high
AAh	Initialization. This command causes the 8042 to inhibit the keyboard and pointing device and
	places 55h into the output buffer.
ABh	Test the clock and data lines of the keyboard interface and place test results in the output buffer.
	00h = No error detected
	01h = Clock line stuck low
	02h = Clock line stuck high
	03h = Data line stuck low
	04h = Data line stuck high
ADh	Disable keyboard command (sets bit <4> of the 8042 command byte).
AEh	Enable keyboard command (clears bit <4> of the 8042 command byte).
C0h	Read input port of the 8042. This command directs the 8042 to transfer the contents of the input
	port to the output buffer so that they can be read at port 60h.
C2h	Poll Input Port High. This command directs the 8042 to place bits <7..4> of the input port into the
	upper half of the status byte on a continous basis until another command is received.
C3h	Poll Input Port Low. This command directs the 8042 to place bits <3..0> of the input port into the
	lower half of the status byte on a continous basis until another command is received.
D0h	Read output port. This command directs the 8042 to transfer the contents of the output port to the
	output buffer so that they can be read at port 60h.
D1h	Write output port. This command directs the 8042 to place the next byte written to port 60h into
	the output port (only bit <1> can be changed).
D2h	Echo keyboard data. Directs the 8042 to send back to the CPU the next byte written to port 60h
	as if it originated from the keyboard. No 11-to-9 bit translation takes place but an interrupt
	(IRQ1) is generated if enabled.
D3h	Echo pointing device data. Directs the 8042 to send back to the CPU the next byte written to port
	60h as if it originated from the pointing device. An interrupt (IRQ12) is generated if enabled.
D4h	Write to pointing device. Directs the 8042 to send the next byte written to 60h to the pointing
	device.
E0h	Read test inputs. Directs the 8042 to transfer the test bits 1 and 0 into bits <1,0> of the output
	buffer.
F0h-FFh	Pulse output port. Controls the pulsing of bits <3..0> of the output port (0 = pulse, 1 = don’t
	pulse). Note that pulsing bit <0> will reset the system.

5-20 www.hp.com Technical Reference Guide