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MOTOROLA
MC68306 USER'S MANUAL
ix
TABLE OF CONTENTS (Continued)
Paragraph
Page
Number
Title
Number
6.2.8.1 RTSB ................................................................................................................
6-6
6.2.8.2 OP1...................................................................................................................
6-6
6.2.9 Channel A Clear-To-Send (CTSA/IP0) ................................................................
6-6
6.2.9.1 CTSA ................................................................................................................
6-6
6.2.9.2 IP0 ....................................................................................................................
6-6
6.2.10 Channel B Clear-To-Send (CTSB/IP1) ..............................................................
6-6
6.2.10.1 CTSB ..............................................................................................................
6-6
6.2.10.2 IP1 ..................................................................................................................
6-6
6.3 Operation ................................................................................................................
6-7
6.3.1 Baud Rate Generator...........................................................................................
6-7
6.3.2 Transmitter and Receiver Operating Modes ........................................................
6-7
6.3.2.1 Transmitter ........................................................................................................
6-9
6.3.2.2 Receiver............................................................................................................
6-10
6.3.2.3 FIFO Stack ........................................................................................................
6-11
6.3.3 Looping Modes ....................................................................................................
6-13
6.3.3.1 Automatic Echo Mode.......................................................................................
6-13
6.3.3.2 Local Loopback Mode.......................................................................................
6-13
6.3.3.3 Remote Loopback Mode ...................................................................................
6-13
6.3.4 Multidrop Mode ....................................................................................................
6-14
6.3.5 Counter/Timer ......................................................................................................
6-16
6.3.5.1 Counter Mode ...................................................................................................
6-16
6.3.5.2 Timer Mode.......................................................................................................
6-16
6.3.6 Bus Operation ......................................................................................................
6-17
6.3.6.1 Read Cycles ................................................................................................ .....
6-17
6.3.6.2 Write Cycles......................................................................................................
6-17
6.3.6.3 Interrupt Acknowledge Cycles ..........................................................................
6-17
6.4 Register Description and Programming ..................................................................
6-17
6.4.1 Register Description ............................................................................................
6-17
6.4.1.1 Mode Register 1 (DUMR1) ...............................................................................
6-18
6.4.1.2 Mode Register 2 (DUMR2) ...............................................................................
6-20
6.4.1.3 Status Register (DUSR)....................................................................................
6-22
6.4.1.4 Clock-Select Register (DUCSR) .......................................................................
6-24
6.4.1.5 Command Register (DUCR) .............................................................................
6-26
6.4.1.6 Receiver Buffer (DURB) ...................................................................................
6-29
6.4.1.7 Transmitter Buffer (DUTB) ................................................................................
6-29
6.4.1.8 Input Port Change Register (DUIPCR) .............................................................
6-29
6.4.1.9 Auxiliary Control Register (DUACR) ................................................................
6-30
6.4.1.10 Interrupt Status Register (DUISR) ..................................................................
6-31
6.4.1.11 Interrupt MASK Register (DUIMR)..................................................................
6-33
6.4.1.12 Count Register Current MSB of Counter (DUCUR) ........................................
6-33
6.4.1.13 Count Register Current LSB of Counter (DUCLR) .........................................
6-33
6.4.1.14 Counter/Timer Upper Preload Register (CTUR) .............................................
6-34