Datasheet
187
8246B–AVR–09/11
ATtiny2313A/4313
21.2.2 Considerations for Efficient Programming
Loaded commands and addresses are retained in the device during programming. For efficient
programming, the following should be considered.
• When writing or reading multiple memory locations, the command needs only be loaded
once
• 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
• 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
21.2.3 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 XTAL1 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.
21.2.4 Programming the Flash
Flash is organized in pages, as shown in Table 21-1 on page 184. 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 XTAL1 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 XTAL1 a positive pulse. This loads the address low byte.
C. Load Data Low Byte