ATmega48 Automotive Atmel Corporation, ATmega48 Automotive Datasheet - Page 272

• Manufacturer Part Number: ATmega48 Automotive
• Manufacturer: Atmel Corporation

Specifications of ATmega48 Automotive

• Flash (kbytes): 4 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 23
• Ext Interrupts: 24
• Usb Speed: No
• Usb Interface: No
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 0.5
• Eeprom (bytes): 256
• Self Program Memory: NO
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 125
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 6
• Input Capture Channels: 1
• Pwm Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

24.7.6
24.7.7
24.7.8
24.7.9
272
ATmega48/88/168 Automotive
Prevent Reading the RWW Section During Self-Programming
Setting the Boot Loader Lock Bits by SPM
EEPROM Write Prevents Writing to SPMCSR
Reading the Fuse and Lock Bits from Software
During Self-Programming (either Page Erase or Page Write), the RWW section is always
blocked for reading. The user software itself must prevent that this section is addressed during
the self programming operation. The RWWSB in the SPMCSR will be set as long as the RWW
section is busy. During Self-Programming the Interrupt Vector table should be moved to the BLS
as described in
addressing the RWW section after the programming is completed, the user software must clear
the RWWSB by writing the RWWSRE. See
on page 274
To set the Boot Loader Lock bits, write the desired data to R0, write “X0001001” to SPMCSR
and execute SPM within four clock cycles after writing SPMCSR. The only accessible Lock bits
are the Boot Lock bits that may prevent the Application and Boot Loader section from any soft-
ware update by the MCU.
See
Flash access.
If bits 5..2 in R0 are cleared (zero), the corresponding Boot Lock bit will be programmed if an
SPM instruction is executed within four cycles after BLBSET and SELFPRGEN are set in
SPMCSR. The Z-pointer is don’t care during this operation, but for future compatibility it is rec-
ommended to load the Z-pointer with 0x0001 (same as used for reading the lO
compatibility it is also recommended to set bits 7, 6, 1, and 0 in R0 to “1” when writing the Lock
bits. When programming the Lock bits the entire Flash can be read during the operation.
Note that an EEPROM write operation will block all software programming to Flash. Reading the
Fuses and Lock bits from software will also be prevented during the EEPROM write operation. It
is recommended that the user checks the status bit (EEPE) in the EECR Register and verifies
that the bit is cleared before writing to the SPMCSR Register.
It is possible to read both the Fuse and Lock bits from software. To read the Lock bits, load the
Z-pointer with 0x0001 and set the BLBSET and SELFPRGEN bits in SPMCSR. When an LPM
instruction is executed within three CPU cycles after the BLBSET and SELFPRGEN bits are set
in SPMCSR, the value of the Lock bits will be loaded in the destination register. The BLBSET
and SELFPRGEN bits will auto-clear upon completion of reading the Lock bits or if no LPM
instruction is executed within three CPU cycles or no SPM instruction is executed within four
CPU cycles. When BLBSET and SELFPRGEN are cleared, LPM will work as described in the
Instruction set Manual.
Bit
R0
Bit
Rd
Table 24-2
for an example.
and
“Watchdog Timer” on page
7
1
7
–
Table 24-3
6
1
6
–
for how the different settings of the Boot Loader bits affect the
BLB12
BLB12
5
5
BLB11
BLB11
“Simple Assembly Code Example for a Boot Loader”
4
4
47, or the interrupts must be disabled. Before
BLB02
BLB02
3
3
BLB01
BLB01
2
2
LB2
1
1
1
ck
bits). For future
LB1
0
1
0
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