AR-B1375/AR-B1376 User
’
s Guide
2-2
2.3 KEYBOARD CONTROLLER
The 8042 processor is programmed to support the keyboard serial interface. The keyboard controller receives
serial data from the keyboard, checks its parity, translates scan codes, and presents it to the system as a byte data
in its output buffer. The controller can interrupt the system when data is placed in its output buffer, or wait for the
system to poll its status register to determine when data is available.
Data can be written to the keyboard by writing data to the output buffer of the keyboard controller.
Each byte of data is sent to the keyboard controller in series with an odd parity bit automatically inserted. The
keyboard controller is required to acknowledge all data transmissions. Therefore, another byte of data will not be
sent to keyboard controller until acknowledgment is received for the previous byte sent. The “output buffer full”
interruption may be used for both send and receive routines.
2.4 INTERRUPT CONTROLLER
The equivalent of two 8259 Programmable Interrupt Controllers (PIC) are included on the AR-B1375/AR-B1376
board. They accept requests from peripherals, resolve priorities on pending interrupts in service, issue interrupt
requests to the CPU, and provide vectors which are used as acceptance indices by the CPU to determine which
interrupt service routine to execute.
Following is the system information of interrupt levels:
IRQ8 : Real time clock
IRQ9 : Rerouting to INT 0Ah from hardware IRQ2
IRQ10 : Spare
IRQ11 : Spare
IRQ12 : Spare
IRQ13 : Math. coprocessor
IRQ14 : Hard disk adapter
IRQ15 : Reserved for watchdog
In
Interrupt Level
NMI
CTRL1
IRQ 0
IRQ 1
IRQ 2
IRQ 3
IRQ 4
IRQ 5
IRQ 6
IRQ 7
CTRL2
Parity check
Description
Serial port 2
Serial port 1
Parallel port 2
Floppy disk adapter
Parallel port 1
System timer interrupt from timer 8254
Keyboard output buffer full
Figure 2-1 Interrupt Controller
