Specifications

Contents
Line Status Register ......................................... 8-26
Interrupt ID Register
......................................... 8-28
Interrupt Enable Register
..................................... 8-30
Modem Control Register
..................................... 8-31
Modem Status Register
...................................... 8-33
Chapter 9. CENTRONICS PRINTER INTERFACE 9-1
OVERVIEW
..................................................... 9-1
PRINTER PORT OUTPUT CHARACTERISTICS
................... 9-3
USING THE PRINTER PORT
..................................... 9-4
REGISTER DEFINITIONS/ADDRESSES
.......................... 9-5
Data Port
.................................................... 9-6
Status Port
................................................... 9-7
Control Port
................................................. 9-8
DISABLING SHARING OF PRINTER PORT SIGNALS
........... 9-12
OPTIONAL PRINTER CABLE PINOUT
.......................... 9-14
PRINTER PORT RESET STATE
................................. 9-15
Chapter 10. REAL-TIME CLOCK (DS 1215) 10-1
OVERVIEW
.................................................... 10-1
OPERATION
................................................... 10-3
TIMECHIP COMPARISON REGISTER DEFINITION
............. 10-5
TIMEKEEPER REGISTER INFORMATION
...................... 10-6
TIMECHIP REGISTER DEFINITION
............................ 10-7
AM/PM 12/24-Hour Mode
................................... 10-8
Oscillator and Reset Bits
..................................... 10-8
Zero Bits
................................................... 10-8
Chapter 11. COUNTER/TIMERS (8254) 11-1
OVERVIEW
.................................................... 11-2
BLOCK DIAGRAM
............................................. 11-3
COUNTER/TIMER ARCHITECTURE
............................ 11-4
OPERATION
................................................... 11-6
Reset State
................................................. 11-6
Programming
............................................... 11-6
Read Operations
............................................. 11-8
Mode Definitions
........................................... 11-16
Operation Common to All Modes
............................ 11-23
Counter Use by STD DOS and STD ROM
.................... 11-25