ATMEGA16U2-16AU Atmel, ATMEGA16U2-16AU Datasheet - Page 237
ATMEGA16U2-16AU
Manufacturer Part Number
ATMEGA16U2-16AU
Description
8-bit Microcontrollers - MCU 16K Flash
Manufacturer
Atmel
Datasheet
1.ATMEGA16U2-16AU.pdf
(310 pages)
Specifications of ATMEGA16U2-16AU
Product Category
8-bit Microcontrollers - MCU
Rohs
yes
Core
AVR
Data Bus Width
8 bit
Program Memory Size
16 KB
Data Ram Size
1.25 KB
Data Rom Size
512 B
Program Memory Type
Flash
Factory Pack Quantity
1250
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23.8.12
23.8.13
7799D–AVR–11/10
Programming Time for Flash when Using SPM
Simple Assembly Code Example for a Boot Loader
Flash corruption can easily be avoided by following these design recommendations (one is
sufficient):
The calibrated RC Oscillator is used to time Flash accesses.
gramming time for Flash accesses from the CPU.
Table 23-7.
Flash write (Page Erase, Page Write, and
write Lock bits by SPM)
1. If there is no need for a Boot Loader update in the system, program the Boot Loader
2. Keep the AVR RESET active (low) during periods of insufficient power supply voltage.
3. Keep the AVR core in Power-down sleep mode during periods of low V
.equ PAGESIZEB = PAGESIZE*2
.org SMALLBOOTSTART
Write_page:
Wrloop:
Lock bits to prevent any Boot Loader software updates.
This can be done by enabling the internal Brown-out Detector (BOD) if the operating
voltage matches the detection level. If not, an external low V
can be used. If a reset occurs while a write operation is in progress, the write operation
will be completed provided that the power supply voltage is sufficient.
vent the CPU from attempting to decode and execute instructions, effectively protecting
the SPMCSR Register and thus the Flash from unintentional writes.
;-the routine writes one page of data from RAM to Flash
; the first data location in RAM is pointed to by the Y pointer
; the first data location in Flash is pointed to by the Z-pointer
;-error handling is not included
;-the routine must be placed inside the Boot space
; (at least the Do_spm sub routine). Only code inside NRWW section can
; be read during Self-Programming (Page Erase and Page Write).
;-registers used: r0, r1, temp1 (r16), temp2 (r17), looplo (r24),
; loophi (r25), spmcrval (r20)
; storing and restoring of registers is not included in the routine
; register usage can be optimized at the expense of code size
;-It is assumed that either the interrupt table is moved to the Boot
; loader section or that the interrupts are disabled.
; Page Erase
ldi
call Do_spm
; re-enable the RWW section
ldi
call Do_spm
; transfer data from RAM to Flash page buffer
ldi
ldi
ld
ld
ldi
spmcrval, (1<<PGERS) | (1<<SPMEN)
spmcrval, (1<<RWWSRE) | (1<<SPMEN)
looplo, low(PAGESIZEB)
loophi, high(PAGESIZEB)
r0, Y+
r1, Y+
spmcrval, (1<<SPMEN)
SPM Programming Time
Symbol
;PAGESIZEB is page size in BYTES, not words
Min Programming Time
;init loop variable
;not required for PAGESIZEB<=256
ATmega8U2/16U2/32U2
3.7 ms
Table 23-7
CC
reset protection circuit
Max Programming Time
shows the typical pro-
CC
. This will pre-
4.5 ms
237
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