
7540 Group User’s Manual
i
Table of contents
CHAPTER 1 HARDWARE
DESCRIPTION ................................................................................................................................ 1-2
 FEATURES ...................................................................................................................................... 1-2
 APPLICATION ................................................................................................................................ 1-2
 PIN CONFIGURATION .................................................................................................................. 1-3
 FUNCTIONAL BLOCK .................................................................................................................. 1-5
 PIN DESCRIPTION ........................................................................................................................ 1-8
 GROUP EXPANSION .................................................................................................................... 1-9
 FUNCTIONAL DESCRIPTION .................................................................................................... 1-11
 I/O Ports .................................................................................................................................. 1-17
 Interrupts ................................................................................................................................. 1-21
 Timers ...................................................................................................................................... 1-24
 Serial I/O ................................................................................................................................. 1-35
 Watchdog Timer ..................................................................................................................... 1-42
 Reset Circuit ........................................................................................................................... 1-43
 Clock Generating Circuit ....................................................................................................... 1-45
 NOTES ON PROGRAMMING ..................................................................................................... 1-49
 Processor Status Register .................................................................................................... 1-49
 Interrupts ................................................................................................................................. 1-49
 Decimal Calculations .............................................................................................................. 1-49
 Ports ......................................................................................................................................... 1-49
 A-D Conversion ...................................................................................................................... 1-49
 CPU Mode Register ............................................................................................................... 1-49
 State Transition ...................................................................................................................... 1-49
 NOTES ON HARDWARE ............................................................................................................ 1-49
 One Time PROM Version ..................................................................................................... 1-49
 s Interrupt ............................................................................................................................... 1-50
 s Timers .................................................................................................................................. 1-50
 s Timer A ............................................................................................................................... 1-50
 s Timer X ............................................................................................................................... 1-50
 s Serial I/O ............................................................................................................................. 1-51
 s A-D Converter .................................................................................................................... 1-51
 ROM PROGRAMMING METHOD .............................................................................................. 1-53
 Interrupt ................................................................................................................................... 1-54
 Timing After Interrupt ............................................................................................................. 1-55