Datasheet

235
ATtiny828 [DATASHEET]
8371A–AVR–08/12
5. Wait until V
CC
actually reaches 4.5 – 5.5V before giving any parallel programming commands.
6. Exit programming mode by powering the device down or by bringing RESET
pin to 0V.
23.2.2 Considerations for Efficient Programming
Loaded commands and addresses are retained in the device during programming. For efficient programming, the
following should be considered.
z When writing or reading multiple memory locations, the command needs only be loaded once
z Do not write the data value 0xFF, since this already is the contents of the entire Flash and EEPROM (unless the
EESAVE Fuse is programmed) after a Chip Erase
z Address high byte needs only be loaded before programming or reading a new 256 word window in Flash or 256
byte EEPROM. This also applies to reading signature bytes
23.2.3 Chip Erase
A Chip Erase must be performed before the Flash and/or EEPROM are reprogrammed. The Chip Erase command will
erase all Flash and EEPROM plus lock bits. If the EESAVE fuse is programmed, the EEPROM is not erased.
Lock bits are not reset until the program memory has been completely erased. Fuse bits are not changed.
The Chip Erase command is loaded as follows:
1. Set XA1, XA0 to “10”. This enables command loading
2. Set BS1 to “0”
3. Set DATA to “1000 0000”. This is the command for Chip Erase
4. Give CLKI a positive pulse. This loads the command
5. Give WR
a negative pulse. This starts the Chip Erase. RDY/BSY goes low
6. Wait until RDY/BSY
goes high before loading a new command
23.2.4 Programming the Flash
Flash is organized in pages, as shown in Table 94 on page 232. When programming the Flash, the program data is first
latched into a page buffer. This allows one page of program data to be programmed simultaneously. The following
procedure describes how to program the entire Flash memory:
A. Load Command “Write Flash”
1. Set XA1, XA0 to “10”. This enables command loading.
2. Set BS1 to “0”.
3. Set DATA to “0001 0000”. This is the command for Write Flash.
4. Give CLKI a positive pulse. This loads the command.
B. Load Address Low byte
1. Set XA1, XA0 to “00”. This enables address loading.
2. Set BS1 to “0”. This selects low address.
3. Set DATA = Address low byte (0x00 – 0xFF).
4. Give CLKI a positive pulse. This loads the address low byte.
C. Load Data Low Byte
1. Set XA1, XA0 to “01”. This enables data loading.
2. Set DATA = Data low byte (0x00 – 0xFF).