Atmel ATmega32M1 User Manual

244
7647H–AVR–03/12
Atmel ATmega16/32/64/M1/C1
18.8.1 User Calibration
The software calibration requires that a calibration value is measured and stored in a register or
EEPROM for each chip. The software calibration can be done utilizing the formula:
T = { [ (ADCH << 8) | ADCL ] - T
OS
} / k
where ADCH & ADCL are the ADC data registers, k is a fixed coefficient and T
OS
is the temper-
ature sensor offset value determined and stored into EEPROM.
18.8.2 Manufacturing Calibration
One can also use the calibration values available in the signature row See “Reading the Signa-
ture Row from Software” on page 289.
The calibration values are determined from values measured during test at room temperature
which is approximatively +25°C and during test at hot temperature which is approximatively
+125°C. Calibration measures are done at V
CC
= 3V and with ADC in internal Vref (2.56V)
mode.
There are two algorithms for determining the Centigrade Temperature
formula 1 for ATmega32 up to rev B
formula 2 for ATmega16/64 and ATmega32 rev C.
formula 1: Temp_C = (((ADC_ts - 273)* TS_Gain) / 128) + TS_Offset [Applicable to devices with
0xFF or 0x42 ('B') in the signature memory at address 0x003F]
formula 2: Temp_C = ((((ADC_ts -(298 - TS_Offset)) * TS_Gain) / 128) + 25 [Applicable to
devices with 0x43 ('C') in the signature memory at address 0x003F]
Where :
Temp_C is the result temperature in degrees centigrade.
ADC_ts is the 10 bit result the ADC returns from reading the temperature sensor.
TS_Gain is the unsigned fixed point 8-bit temperature sensor gain factor in 1/128th units stored
as previously in the signature row at address 0x0007.
TS_Offset is the signed twos complement 7-bit temperature sensor offset reading stored as pre-
viously in the signature row at address 0x0005.
See section 24.7.10 in the ATmega32M1 Automotive datasheet for details of reading the Signa-
ture Row.

Atmel ATmega32M1 Specifications

General

Architecture	8-bit AVR
Flash Memory	32 KB
SRAM	2 KB
EEPROM	1 KB
Clock Speed	16 MHz
GPIO Pins	32
I/O Pins	32
ADC Channels	8
ADC Resolution	10-bit
UART	1
USART	1
SPI	1
I2C	1
PWM Channels	6
CAN	1
Operating Voltage	2.7V - 5.5V
Operating Temperature	-40°C to +85°C
Temperature Range	-40°C to +85°C
Package	44-TQFP, 44-QFN

Summary

Features

AVR CPU Core

Reset and Interrupt Handling

Explanation of interrupt sources, vectors, priority levels, and behavior during interrupt execution.

System Clock

System Clock Prescaler

Details on the CLKPR register for dividing the system clock to reduce power consumption and affect peripheral frequencies.

Power Management and Sleep Modes

8-bit Timer/Counter0 with PWM

Modes of Operation

Detailed explanation of Normal, CTC, and various PWM modes for Timer/Counter0 operation.

Controller Area Network - CAN

CAN Protocol

Explanation of the CAN protocol principles, standards, and message transmission priorities.

Error Management

Description of error detection mechanisms (message and bit level) and fault confinement states.

Analog to Digital Converter - ADC

Features

List of ADC capabilities including resolution, accuracy, conversion time, input channels, and reference voltages.

Starting a Conversion

Procedures for initiating ADC conversions, including single conversion and auto-triggering modes.

debugWIRE On-chip Debug System

Features

Overview of debugWIRE capabilities including program flow control, real-time operation, and symbolic debugging.

Boot Loader Support – Read-While-Write Self-Programming ATmega16/32/64/M1/C1

Self-Programming the Flash

Procedures and considerations for programming the Flash memory using the SPM instruction.

Memory Programming

Program And Data Memory Lock Bits

Fuse Bits

Electrical Characteristics

Absolute Maximum Ratings*

Critical voltage, current, and temperature limits that must not be exceeded for device reliability.

DC Characteristics

Instruction Set Summary

Register Summary