ATmega32U4 Atmel Corporation, ATmega32U4 Datasheet - Page 181

• Manufacturer Part Number: ATmega32U4
• Manufacturer: Atmel Corporation

Specifications of ATmega32U4

• Flash (kbytes): 32 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 14
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 26
• Ext Interrupts: 13
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 12
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 3.3
• Eeprom (bytes): 1024
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 4
• Output Compare Channels: 12
• Input Capture Channels: 2
• Pwm Channels: 8
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

17.1
17.1.1
7766F–AVR–11/10
SS Pin Functionality
Slave Mode
The following code examples show how to initialize the SPI as a Slave and how to perform a
simple reception.
Note:
When the SPI is configured as a Slave, the Slave Select (SS) pin is always input. When SS is
held low, the SPI is activated, and MISO becomes an output if configured so by the user. All
Assembly Code Example
C Code Example
SPI_SlaveInit:
SPI_SlaveReceive:
void SPI_SlaveInit(void)
{
}
char SPI_SlaveReceive(void)
{
}
; Set MISO output, all others input
ldi
out
; Enable SPI
ldi
out
ret
; Wait for reception complete
sbis SPSR,SPIF
rjmp SPI_SlaveReceive
; Read received data and return
in
ret
/* Set MISO output, all others input */
DDR_SPI = (1<<DD_MISO);
/* Enable SPI */
SPCR = (1<<SPE);
/* Wait for reception complete */
while(!(SPSR & (1<<SPIF)))
/* Return Data Register */
return SPDR;
1. See “Code Examples” on page 8.
;
r17,(1<<DD_MISO)
DDR_SPI,r17
r17,(1<<SPE)
SPCR,r17
r16,SPDR
(1)
(1)
ATmega16/32U4
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