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CONTENTS
viii
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 Timer 2-Initiated Transfers ............................................................................10-6
10.1.5.2 Unsynchronized Transfers ............................................................................10-6
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 ......................................................................10-7
10.1.7.2 Software Termination ....................................................................................10-7
10.1.7.3 Suspension of DMA During NMI ...................................................................10-7
10.1.7.4 Software Suspension ....................................................................................10-7
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 Unit ...................................................................................10-8
10.1.10.1 DMA Channel Arbitration ...............................................................................10-8
10.2 PROGRAMMING THE DMA UNIT ............................................................................ 10-10
10.2.1 DMA Channel Parameters ....................................................................................10-10
10.2.1.1 Programming the Source and Destination Pointers ....................................10-10
10.2.1.2 Selecting Byte or Word Size Transfers ........................................................10-14
10.2.1.3 Selecting the Source of DMA Requests ......................................................10-17
10.2.1.4 Arming the DMA Channel ............................................................................10-18
10.2.1.5 Selecting Channel Synchronization .............................................................10-18
10.2.1.6 Programming the Transfer Count Options ...................................................10-18
10.2.1.7 Generating Interrupts on Terminal Count ....................................................10-19
10.2.1.8 Setting the Relative Priority of a Channel ....................................................10-19
10.2.2 Suspension of DMA Transfers ..............................................................................10-20
10.2.3 Initializing the DMA Unit ........................................................................................10-20
10.3 HARDWARE CONSIDERATIONS AND THE DMA UNIT ......................................... 10-20
10.3.1 DRQ Pin Timing Requirements .............................................................................10-20
10.3.2 DMA Latency ........................................................................................................10-21
10.3.3 DMA Transfer Rates .............................................................................................10-21
10.3.4 Generating a DMA Acknowledge ..........................................................................10-22
10.4 DMA UNIT EXAMPLES............................................................................................. 10-22
CHAPTER 11
MATH COPROCESSING
11.1 OVERVIEW OF MATH COPROCESSING.................................................................. 11-1
11.2 AVAILABILITY OF MATH COPROCESSING.............................................................. 11-1
11.3 THE 80C187 MATH COPROCESSOR........................................................................ 11-2
11.3.1 80C187 Instruction Set ...........................................................................................11-2
11.3.1.1 Data Transfer Instructions .............................................................................11-3
11.3.1.2 Arithmetic Instructions ...................................................................................11-3
11.3.1.3 Comparison Instructions ................................................................................11-5