ATmega32U4 Atmel Corporation, ATmega32U4 Datasheet - Page 159

• 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

15.11 Accessing 10-Bit Registers
7766F–AVR–11/10
If 10-bit values are written to the TCNTn and OCRnA/B/C/D registers, the 10-bit registers can be
byte accessed by the AVR CPU via the 8-bit data bus using two read or write operations. The
10-bit registers have a common 2-bit Timer/Counter4 High Byte Register (TC4H) that is used for
temporary storing of the two MSBs of the 10-bit access. The same TC4H register is shared
between all 10-bit registers. Accessing the low byte triggers the 10-bit read or write operation.
When the low byte of a 10-bit register is written by the CPU, the high byte stored in the TC4H
register, and the low byte written are both copied into the 10-bit register in the same clock cycle.
When the low byte of a 10-bit register is read by the CPU, the high byte of the 10-bit register is
copied into the TC4H register in the same clock cycle as the low byte is read.
To do a 10-bit write, the high byte must be written to the TC4H register before the low byte is
written. For a 10-bit read, the low byte must be read before the high byte.
The following code examples show how to access the 10-bit timer registers assuming that no
interrupts updates the TC4H register. The same principle can be used directly for accessing the
OCRnA/B/C/C/D registers.
Note:
The assembly code example returns the TCNTn value in the r17:r16 register pair.
Assembly Code Example
C Code Example
unsigned int i;
...
/* Set TCNTn to 0x01FF */
TCnH = 0x01;
TCNTn = 0xFF;
/* Read TCNTn into i */
i = TCNTn;
i |= ((unsigned int)TCnH << 8);
...
...
; Set TCNTn to 0x01FF
ldi r17,0x01
ldi r16,0xFF
out TCnH,r17
out TCNTn,r16
; Read TCNTn into r17:r16
in r16,TCNTn
in r17,TCnH
...
1. The example code assumes that the part specific header file is included.
For I/O registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and “SBI”
instructions must be replaced with instructions that allow access to extended I/O. Typically
“LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”.
ATmega16/32U4
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