Rainbow Electronics ATmega32L - Manual (Page 269)

269
ATmega32(L)
2503C–AVR–10/02
Chip Erase instruction. The Chip Erase operation turns the content of every memory
location in both the Program and EEPROM arrays into $FF.
Depending on CKSEL Fuses, a valid clock must be present. The minimum low and high
periods for the serial clock (SCK) input are defined as follows:
Low:> 2 CPU clock cycles for f
ck
< 12 MHz, 3 CPU clock cycles for f
ck
≥ 12 MHz
High:> 2 CPU clock cycles for f
ck
< 12 MHz, 3 CPU clock cycles for f
ck
≥ 12 MHz
SPI Serial Programming
Algorithm When writing serial data to the ATmega32, data is clocked on the rising edge of SCK.
When reading data from the ATmega32, data is clocked on the falling edge of SCK. See
Figure 137 for timing details.
To program and verify the ATmega32 in the SPI Serial Programming mode, the follow-
ing sequence is recommended (See four byte instruction formats in Table 116):
1. Power-up sequence:
Apply power between V
CC
and GND while RESET and SCK are set to “0”. In
some systems, the programmer can not guarantee that SCK is held low during
power-up. In this case, RESET must be given a positive pulse of at least two
CPU clock cycles duration after SCK has been set to “0”.
2. Wait for at least 20 ms and enable SPI Serial Programming by sending the Pro-
gramming Enable serial instruction to pin MOSI.
3. The SPI Serial Programming instructions will not work if the communication is
out of synchronization. When in sync. the second byte ($53), will echo back
when issuing the third byte of the Programming Enable instruction. Whether the
echo is correct or not, all four bytes of the instruction must be transmitted. If the
$53 did not echo back, give RESET a positive pulse and issue a new Program-
ming 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 6 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 8 MSB of the address. If polling is not used,
the user must wait at least t
WD_FLASH
before issuing the next page. (See Table
115). Accessing the SPI 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 115). In a chip erased device, no $FFs 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 MISO.
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.