80C186EC/80C188EC Microprocessor User's Manual

CONTENTS
CHAPTER 9
TIMER/COUNTER UNIT
9.1 FUNCTIONAL OVERVIEW............................................................................................ 9-1
9.2 PROGRAMMING THE TIMER/COUNTER UNIT .......................................................... 9-6
9.2.1 Initialization Sequence ............................................................................................9-11
9.2.2 Clock Sources .........................................................................................................9-12
9.2.3 Counting Modes ......................................................................................................9-12
9.2.3.1 Retriggering ...................................................................................................9-13
9.2.4 Pulsed and Variable Duty Cycle Output ..................................................................9-14
9.2.5 Enabling/Disabling Counters ...................................................................................9-15
9.2.6 Timer Interrupts .......................................................................................................9-16
9.2.7 Programming Considerations ..................................................................................9-16
9.3 TIMING ........................................................................................................................ 9-16
9.3.1 Input Setup and Hold Timings .................................................................................9-16
9.3.2 Synchronization and Maximum Frequency .............................................................9-17
9.3.2.1 Timer/Counter Unit Application Examples .....................................................9-17
9.3.3 Real-Time Clock .....................................................................................................9-17
9.3.4 Square-Wave Generator .........................................................................................9-17
9.3.5 Digital One-Shot ......................................................................................................9-17
CHAPTER 10
DIRECT MEMORY ACCESS UNIT
10.1 FUNCTIONAL OVERVIEW.......................................................................................... 10-1
10.1.1 The DMA Transfer ..................................................................................................10-1
10.1.1.1 DMA Transfer Directions ...............................................................................10-3
10.1.1.2 Byte and Word Transfers ..............................................................................10-3
10.1.2 Source and Destination Pointers ............................................................................10-3
10.1.3 DMA Requests ........................................................................................................10-3
10.1.4 External Requests ...................................................................................................10-4
10.1.4.1 Source Synchronization ................................................................................10-5
10.1.4.2 Destination Synchronization ..........................................................................10-5
10.1.5 Internal Requests ....................................................................................................10-6
10.1.5.1 Integrated Peripheral Requests .....................................................................10-6
10.1.5.2 Timer 2-Initiated Transfers ............................................................................10-6
10.1.5.3 Serial Communications Unit Transfers ..........................................................10-7
10.1.5.4 Unsynchronized Transfers ............................................................................10-7
10.1.6 DMA Transfer Counts .............................................................................................10-7
10.1.7 Termination and Suspension of DMA Transfers .....................................................10-7
10.1.7.1 Termination at Terminal Count ......................................................................10-8
10.1.7.2 Software Termination ....................................................................................10-8
10.1.7.3 Suspension of DMA During NMI ...................................................................10-8
10.1.7.4 Software Suspension ....................................................................................10-8
10.1.8 DMA Unit Interrupts ................................................................................................10-8
10.1.9 DMA Cycles and the BIU ........................................................................................10-8
10.1.10 The Two-Channel DMA Module ..............................................................................10-9
10.1.10.1 DMA Channel Arbitration ...............................................................................10-9
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