Datasheet

369
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
instruction. Whether the echo is correct or not, all four bytes of the instruction must be transmitted. If the
0x53 did not echo back, give RESET
a positive pulse and issue a new Programming Enable command.
4. The Flash is programmed one page at a time. The memory page is loaded one byte at a time by supplying
the seven LSB of the address and data together with the Load Program Memory Page instruction. To
ensure correct loading of the page, the data low byte must be loaded before data high byte is applied for a
given address. The Program Memory Page is stored by loading the Write Program Memory Page
instruction with the address lines 15..8. Before issuing this command, make sure the instruction Load
Extended Address Byte has been used to define the MSB of the address. The extended address byte is
stored until the command is re-issued, i.e., the command needs only be issued for the first page, and
when crossing the 64KWord boundary. If polling (RDY/BSY
) is not used, the user must wait at least
t
WD_FLASH
before issuing the next page. (See Table 28-15 on page 369.) Accessing the serial programming
interface before the Flash write operation completes can result in incorrect programming.
5. The EEPROM array is programmed one byte at a time by supplying the address and data together with
the appropriate Write instruction. An EEPROM memory location is first automatically erased before new
data is written. If polling is not used, the user must wait at least t
WD_EEPROM
before issuing the next byte.
(See
Table 28-15 on page 369.) In a chip erased device, no 0xFFs in the data file(s) need to be
programmed.
6. Any memory location can be verified by using the Read instruction which returns the content at the
selected address at serial output PDO. When reading the Flash memory, use the instruction Load
Extended Address Byte to define the upper address byte, which is not included in the Read Program
Memory instruction. The extended address byte is stored until the command is re-issued, i.e., the
command needs only be issued for the first page, and when crossing the 64KWord boundary.
7. At the end of the programming session, RESET
can be set high to commence normal operation.
8. Power-off sequence (if needed):
Set RESET
to “1”.
Turn V
CC
power off.
Figure 28-11. Serial Programming Waveforms
Table 28-15. Minimum Wait Delay Before Writing the Next Flash or EEPROM
Symbol Minimum Wait Delay
t
WD_FLASH
4.5ms
t
WD_EEPROM
9.0ms
t
WD_ERASE
9.0ms
MSB
MSB
LSB
LSB
SERIAL CLOCK INPUT
(SCK)
SERIAL DATA INPUT
(MOSI)
(MISO)
SAMPLE
SERIAL DATA OUTPUT