8259A: Top Choice in United States (USA) Utsource Holding Company Limited

Description

Parameter	Description
Device Name	8259A Programmable Interrupt Controller
Function	Manages interrupt requests from peripheral devices to the CPU
Number of IRQs	Can handle up to 8 interrupt request lines (IRQ0-IRQ7)
Cascading Capability	Multiple 8259A chips can be cascaded to increase the number of IRQ lines
Operating Modes	Fully Nested Mode, Special Mask Mode, Auto EOI Mode, Simple Mode
Control Word Length	Initialization Control Words (ICW1-ICW4), Operation Control Words (OCW1-OCW3)
Power Supply	+5V DC
Temperature Range	Commercial: 0°C to +70°C, Military: -55°C to +125°C

ICW1:
- Sets the edge/level trigger mode and indicates that ICWs will follow.
- Bit 4 (IC4): 1 if ICW4 is required, 0 otherwise.
- Bits 0-3: Set to 1111 for initialization.
ICW2:
- Specifies the base interrupt vector address.
- Vector addresses are used by the CPU to branch to the appropriate ISR.
ICW3:
- Used in cascade configurations.
- Specifies which IR lines are connected to slave 8259A devices.
ICW4:
- Sets special fully nested mode and auto EOI mode.
- Determines the type of microprocessor interface.

OCW1:
- Masks individual interrupt request lines.
- Each bit corresponds to an IR line; setting a bit masks the corresponding interrupt.
OCW2:
- Controls the priority and end-of-interrupt (EOI) functions.
- Options include non-specific EOI, specific EOI, rotate on specific EOI, and rotate on every EOI.
OCW3:
- Configures special features like polling and read_ISR operation.
- Allows reading of the in-service register or polling register.

Ensure proper sequencing of ICWs during initialization.
Use OCWs to dynamically control interrupt masking and prioritization as needed.
When cascading multiple 8259A chips, correctly configure ICW3 to specify connections between master and slave devices.

(For reference only)