202
8008H–AVR–04/11
ATtiny48/88
21.3.1
Pin Mapping
21.3.2
Programming Algorithm
When writing serial data to the ATtiny48/88, data is clocked on the rising edge of SCK. When
reading data from the ATtiny48/88, data is clocked on the falling edge of SCK. See
Figure 22-9To program and verify the ATtiny48/88 in the serial programming mode, the following sequence
):
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 after SCK has been
set to '0'. The duration of the pulse must be at least t
RST plus two CPU clock cycles.
t
RST
2.
Wait for at least 20 ms and enable serial programming by sending the Programming
Enable serial instruction to pin MOSI.
3.
The serial programming instructions will not work if the communication is out of syn-
chronization. When in sync. the second byte (0x53), 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 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 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 7 MSB of the address.
– If polling (RDY/BSY) is not used, the user must wait at least t
WD_FLASH before issuing
the next page (See
Table 21-9). Accessing the serial programming interface before
the Flash write operation completes can result in incorrect programming.
5.
The EEPROM can be programmed one byte or one page at a time.
– A: 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 (RDY/BSY)
is not used, the user must wait at least t
WD_EEPROM before issuing the next byte (See
Table 21-7.
Pin Mapping Serial Programming
Symbol
Pins
I/O
Description
MOSI
PB3
I
Serial Data in
MISO
PB4
O
Serial Data out
SCK
PB5
I
Serial Clock