Acrosser AR-B1550 User Manual
Page 9
AR-B1550 User
s Guide
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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-B1550 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 interrupt levels:
IRQ2
Interrupt Level
Description
NMI
Parity check
CTRL1
IRQ0
IRQ1
System timer interrupt from timer 8254
keyboard output buffer full
Rerouting to IRQ8 to IRQ15
CTRL2
IRQ8:Real time clock
IRQ9:Reserved
IRQ10:LAN adapters(based on PCI INT routing)
IRQ12:Reserved for PS/2 mouse
IRQ11:LAN adapters(based on PCI INT routing)
IRQ13:Math.Co-processor
IRQ14: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
IRQ15:LAN adapters(based on PCI INT routing
Interrupt Controller
2.4.1 I/O Port Address Map
Hex Range
Device
000-01F
DMA controller 1
020-021
Interrupt controller 1
022-023
Cyrix CS5530
040-04F
Timer 1