Sony AR-B1570 manual Keyboard Controller, Interrupt Controller

AR-B1570 User’s Guide

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 a 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-B1570 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. These two controllers are cascaded with the second controller representing IRQ8 to IRQ15, which is rerouted through IRQ2 on the first controller.

The following is the system information of interrupts levels:

Interrupt Level

NMI

CTRL1 CTRL2 IRQ0

IRQ1

IRQ2

Description

Parity check

System timer interrupt from timer 8254 keyboard output buffer full Rerouting to IRQ8 to IRQ15

	IRQ8:Real time clock
	IRQ9:Reserved
	IRQ10:LAN adapters(based on PCI INT routing)
	IRQ12:Reserved for PS/2 mouse
	IRQ13:Math.Co-processor
	IRQ14:Hard disk adapter
	IRQ15:Hard disk adapter
IRQ3	Serial port(depends on setup assignment)
IRQ4	Serial port(depends on setup assignment)
IRQ5	Reserved
IRQ6	Reserved for floppy disk adapter
IRQ7	Parallel port 1
	Interrupt Controller

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