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CHAPTER 10 I/O PORTS
10.1
I/O Ports
Each pin of the ports can be specified as input or output using the direction register if
the corresponding peripheral does not use the pin. When a pin is specified as input, the
logic level at the pin is read. When a pin is specified as output, the data register value is
read. The above also applies to a read operation for the read-modify-write (RMW)
instructions.
■
I/O Ports
When a pin is used as an output of other peripheral function, the peripheral output value is read regardless
of the direction register value.
It is generally recommended that the read-modify-write (RMW) instructions should not be used for setting
the data register prior to setting the port as an output. This is because the read-modify-write (RMW)
instruction in this case results reading the logic level at the port rather than the register value.
Figure 10.1-1 is a block diagram of the I/O ports.
Figure 10.1-1 I/O Port Block Diagram
Internal data bus
Data register read
Data register
w
rite
Direction register
w
rite
Direction register read
Data register
Direction register
Pin
Summary of Contents for MB90390 Series
Page 2: ......
Page 4: ......
Page 17: ...xiii APPENDIX D List of Interrupt Vectors 690 INDEX 695 ...
Page 18: ...xiv ...
Page 132: ...104 CHAPTER 5 CLOCKS ...
Page 152: ...124 CHAPTER 6 CLOCK MODULATOR ...
Page 210: ...182 CHAPTER 11 TIME BASE TIMER ...
Page 218: ...190 CHAPTER 12 WATCHDOG TIMER ...
Page 264: ...236 CHAPTER 14 16 BIT RELOAD TIMER WITH EVENT COUNT FUNCTION ...
Page 274: ...246 CHAPTER 15 WATCH TIMER ...
Page 306: ...278 CHAPTER 17 DTP EXTERNAL INTERRUPTS ...
Page 338: ...310 CHAPTER 18 8 10 BIT A D CONVERTER ...
Page 364: ...336 CHAPTER 19 UART0 UART1 ...
Page 398: ...370 CHAPTER 20 UART2 UART3 Figure 20 5 2 ORE Set Timing Receive data RDRF ORE ...
Page 432: ...404 CHAPTER 20 UART2 UART3 ...
Page 482: ...454 CHAPTER 22 SERIAL I O ...
Page 560: ...532 CHAPTER 24 STEPPING MOTOR CONTROLLER ...
Page 582: ...554 CHAPTER 27 ROM MIRRORING MODULE ...
Page 632: ...604 CHAPTER 29 EXAMPLES OF SERIAL PROGRAMMING CONNECTION ...
Page 722: ...694 APPENDIX ...
Page 723: ...695 INDEX The index follows on the next page This is listed in alphabetic order ...
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