HP Dc7700 HP Compaq dx7300 and dc7700 Business PC Technical Reference Guide, 1 - Page 98

Input/Output Interfaces Value A9h AAh ABh ADh AEh C0h C2h C3h D0h D1h D2h D3h D4h E0h F0h-FFh Table 5-15. (Continued) CPU Commands to the 8042 Command Description 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 Initialization. This command causes the 8042 to inhibit the keyboard and pointing device and places 55h into the output buffer. 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 Disable keyboard command (sets bit of the 8042 command byte). Enable keyboard command (clears bit of the 8042 command byte). 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. Poll Input Port High. This command directs the 8042 to place bits of the input port into the upper half of the status byte on a continous basis until another command is received. Poll Input Port Low. This command directs the 8042 to place bits of the input port into the lower half of the status byte on a continous basis until another command is received. 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. Write output port. This command directs the 8042 to place the next byte written to port 60h into the output port (only bit can be changed). 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. 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. Write to pointing device. Directs the 8042 to send the next byte written to 60h to the pointing device. Read test inputs. Directs the 8042 to transfer the test bits 1 and 0 into bits of the output buffer. Pulse output port. Controls the pulsing of bits of the output port (0 = pulse, 1 = don't pulse). Note that pulsing bit will reset the system. 5-20 www.hp.com Technical Reference Guide