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175

8025I–AVR–02/09

ATmega48P/88P/168P/328P

16.5.3 SPDR – SPI Data Register

The SPI Data Register is a read/write register used for data transfer between the Register File

and the SPI Shift Register. Writing to the register initiates data transmission. Reading the regis-

ter causes the Shift Register Receive buffer to be read.

Bit 76543210

0x2E (0x4E) MSB LSB SPDR

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial ValueXXXXXXXXUndefined

Default Chapter1
- Features1
1 Pin Configurations2
- Pin Descriptions3
2 Overview4
- Block Diagram5
- Comparison between Atmega48P, Atmega88P, Atmega168P, and Atmega328P6
3 About7
- Disclaimer7
- Resources7
- Data Retention7
- Code Examples7
4 AVR CPU Core8
- Overview8
- ALU - Arithmetic Logic Unit9
- Status Register9
- General Purpose Register File11
- Stack Pointer12
- Instruction Execution Timing13
- Reset and Interrupt Handling14
5 AVR Memories16
- Overview16
- In-System Reprogrammable Flash Program Memory16
- SRAM Data Memory18
- EEPROM Data Memory19
- I/O Memory20
- Register Description21
6 System Clock and Clock Options26
- Clock Systems and Their Distribution26
- Clock Sources27
- Low Power Crystal Oscillator28
- Full Swing Crystal Oscillator30
- Low Frequency Crystal Oscillator32
- Calibrated Internal RC Oscillator33
- Khz Internal Oscillator33
- External Clock34
- Clock Output Buffer35
- Timer/Counter Oscillator35
- System Clock Prescaler35
- Register Description37
7 Power Management and Sleep Modes39
- Sleep Modes39
- BOD Disable40
- Idle Mode40
- ADC Noise Reduction Mode40
- Power-Down Mode41
- Power-Save Mode41
- Standby Mode41
- Extended Standby Mode41
- Power Reduction Register42
- Minimizing Power Consumption42
- Register Description44
8 System Control and Reset46
- Resetting the AVR46
- Reset Sources46
- Power-On Reset47
- External Reset48
- Brown-Out Detection48
- Watchdog System Reset49
- Internal Voltage Reference49
- Watchdog Timer50
- Register Description54
9 Interrupts57
- Interrupt Vectors in Atmega48P57
- Interrupt Vectors in Atmega88P59
- Interrupt Vectors in Atmega168P62
- Interrupt Vectors in Atmega328P65
- Register Description68
10 External Interrupts70
- Pin Change Interrupt Timing70
- Register Description71
11 O-Ports75
- Overview75
- Ports as General Digital I/O76
- Alternate Port Functions80
- Register Description92
12 8-Bit Timer/Counter0 with PWM94
- Features94
- Overview94
- Timer/Counter Clock Sources96
- Counter Unit96
- Output Compare Unit97
- Compare Match Output Unit98
- Modes of Operation99
- Timer/Counter Timing Diagrams104
- Register Description106
16 Bit Timer/Counter1 with PWM113
- Features113
- Overview113
- Accessing 16-Bit Registers115
- Timer/Counter Clock Sources118
- Counter Unit119
- Input Capture Unit120
- Output Compare Units122
- Compare Match Output Unit124
- Modes of Operation125
- Timer/Counter Timing Diagrams132
- Register Description134
14 Timer/Counter0 and Timer/Counter1 Prescalers141
- Internal Clock Source141
- Prescaler Reset141
- External Clock Source141
- Register Description143
15 8-Bit Timer/Counter2 with PWM and Asynchronous Operation144
- Features144
- Overview144
- Timer/Counter Clock Sources145
- Counter Unit145
- Output Compare Unit146
- Compare Match Output Unit148
- Modes of Operation149
- Timer/Counter Timing Diagrams153
- Asynchronous Operation of Timer/Counter2155
- Timer/Counter Prescaler156
- Register Description158
16 SPI - Serial Peripheral Interface166
- Features166
- Overview166
- SS Pin Functionality171
- Data Modes171
- Register Description173
17 Usart0176
- Features176
- Overview176
- Clock Generation177
- Frame Formats180
- USART Initialization182
- Data Transmission - the USART Transmitter183
- Data Reception - the USART Receiver186
- Asynchronous Data Reception190
- Multi-Processor Communication Mode193
- Register Description195
- Examples of Baud Rate Setting199
18 USART in SPI Mode204
- Features204
- Overview204
- Clock Generation204
- SPI Data Modes and Timing205
- Frame Formats206
- Data Transfer208
- AVR USART MSPIM Vs. AVR SPI210
- Register Description211
19 2-Wire Serial Interface214
- Features214
- Wire Serial Interface Bus Definition214
- Data Transfer and Frame Format216
- Multi-Master Bus Systems, Arbitration and Synchronization218
- Overview of the TWI Module221
- Using the TWI223
- Transmission Modes227
- Multi-Master Systems and Arbitration240
- Register Description241
20 Analog Comparator246
- Overview246
- Analog Comparator Multiplexed Input246
- Register Description247
21 Analog-To-Digital Converter250
- Features250
- Overview250
- Starting a Conversion252
- Prescaling and Conversion Timing253
- Changing Channel or Reference Selection255
- ADC Noise Canceler256
- ADC Conversion Result261
- Temperature Measurement261
- Register Description262
22 Debugwire On-Chip Debug System267
- Features267
- Overview267
- Physical Interface267
- Software Break Points268
- Limitations of Debugwire268
- Register Description268
23 Self-Programming the Flash, Atmega48P269
- Overview269
- Addressing the Flash During Self-Programming270
- Register Description275
24 Boot Loader Support - Read-While-Write Self-Programming, Atmega88P, Atmega168P and Atmega328P277
- Features277
- Overview277
- Application and Boot Loader Flash Sections277
- Read-While-Write and no Read-While-Write Flash Sections278
- Boot Loader Lock Bits280
- Entering the Boot Loader Program281
- Addressing the Flash During Self-Programming282
- Self-Programming the Flash282
- Register Description292
25 Memory Programming294
- Program and Data Memory Lock Bits294
- Fuse Bits295
- Signature Bytes298
- Calibration Byte299
- Page Size299
- Parallel Programming Parameters, Pin Mapping, and Commands299
- Parallel Programming301
- Serial Downloading308
26 Electrical Characteristics313
- Absolute Maximum Ratings313
- DC Characteristics313
- Speed Grades316
- Clock Characteristics319
- System and Reset Characteristics320
- SPI Timing Characteristics321
- Wire Serial Interface Characteristics323
- ADC Characteristics - Preliminary Data325
- Parallel Programming Characteristics326
27 Typical Characteristics328
- Atmega48P Typical Characteristics329
- Atmega88P Typical Characteristics353
- Atmega168P Typical Characteristics377
- Atmega328P Typical Characteristics401
28 Register Summary425
29 Instruction Set Summary429
30 Ordering Information432
- Atmega48P432
- Atmega88P433
- Atmega168P434
- Atmega328P435
31 Packaging Information436
- M1-A438
32 Errata440
- Errata Atmega48P440
- Errata Atmega88P440
- Errata Atmega168P440
- Errata Atmega328P440
33 Datasheet Revision History442
- Rev. 2545I-02/09442
- Rev. 2545H-02/09442
- Rev. 2545G-01/09442
- Rev. 2545F-08/08443
- Rev. 2545E-08/08443
- Rev. 2545D-03/08443
- Rev. 2545C-01/08443
- Rev. 2545B-01/08444
- Rev. 2545A-07/07444

Brand	Atmel
Model	ATmega48PV
Category	Microcontrollers
Language	English

Atmel ATmega48PV User Manual

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Atmel ATmega48PV Specifications

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