Rainbow Electronics ATmega103L - Manual (Page 95)

ATmega603/103
95
Enter Programming Mode
The following algorithm puts the device in parallel programming mode:
1. Apply supply voltage according to Table 37, between V
CC
and GND.
2. Set RESET and BS1 pins to ‘0’ and wait at least 100 ns.
3. Apply 11.5 - 12.5V to RESET. Any activity on BS1 within 100 ns after +12V has been applied to RESET, will cause
the device to fail entering programming mode.
Chip Erase
The Chip Erase will erase the Flash and EEPROM memories, and Lock bits. The Lock bits are not reset until the program
memory has been completely erased. The Fuse bits are not changed. A chip erase must be performed before the Flash or
EEPROM is reprogrammed.
Load Command “Chip Erase”
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 t
WLWH_CE
wide negative pulse to execute Chip Erase. See Table 41 for t
WLWH_CE
value. Chip Erase does
not generate any activity on the RDY/BSY pin.
Table 40. Command Byte Bit Coding
Command Byte Command Executed
1000 0000 Chip Erase
0100 0000 Write Fuse Bits
0010 0000 Write Lock Bits
0001 0000 Write Flash
0001 0001 Write EEPROM
0000 1000 Read Signature Bytes
0000 0100 Read Lock and Fuse Bits
0000 0010 Read Flash
0000 0011 Read EEPROM
Table 41. Minimum WR pulse width for chip erase
Symbol 3.2V 3.6V 4.0V 5.0V
t
WLWH_CE
56 ms 43 ms 35 ms 22 ms