Specifications

Contents
Chapter 12. INTERRUPT CONTROLLER (8259A) 12-1
OVERVIEW
.................................................... 12-3
I/O PORT ADDRESSES
......................................... 12-3
OPERATION OVERVIEW
....................................... 12-4
FUNCTIONAL DESCRIPTION
.................................. 12-7
Interrupt Request Register (IRR)
.............................. 12-8
Interrupt Mask Register (IMR)
................................ 12-8
Priority Resolver (PR)
....................................... 12-9
Interrupt In-Service Register (ISR)
............................ 12-9
Control Logic
............................................... 12-9
Read/Write Control Logic
................................... 12-10
Initialization and Operation Registers
......................... 12-10
Cascade Buffer/Comparator
................................. 12-10
PROGRAMMABLE REGISTERS
............................... 12-11
Initialization Control Words (ICW1-4)
........................ 12-12
Operation Control Words (OCW1-3)
......................... 12-16
8259A I/O PORT ADDRESSES
................................. 12-21
INTERRUPT ASSIGNMENTS ON THE ZT 8809A
............... 12-22
OPERATION OF THE INTERRUPT CONTROLLER
............. 12-24
Priorities
.................................................. 12-24
Interrupt Triggering
........................................ 12-27
Interrupt Status
............................................ 12-29
EOI COMMANDS
............................................. 12-31
Nonspecific EOI Commands
................................ 12-31
Specific EOI Commands
.................................... 12-32
Automatic EOI Mode
....................................... 12-32
RESET
........................................................ 12-34
Chapter 13. ZT 88CT08A/88CT09A CMOS BOARDS 13-1
OVERVIEW
.................................................... 13-1
FUNCTIONAL DIFFERENCES
.................................. 13-2
Logic Family (CT vs. C)
..................................... 13-2
Use of 80C88 Processor
...................................... 13-3
Addition of Optional 8087(-2)
................................ 13-4
Clock Slowdown Mode
...................................... 13-4
Halt With Restart Via Interrupt
................................ 13-6
ELECTRICAL/ENVIRONMENTAL DIFFERENCES
.............. 13-8
Increased Temperature Range
................................. 13-8
Reduced Power Consumption
................................. 13-8
Bus Loading
................................................ 13-9