Rainbow Electronics ATmega64C1 - Manual (Page 305)

305
7647A–AVR–02/08
ATmega32/64/M1/C1
Notes: 1. t
WLRH
is valid for the Write Flash, Write EEPROM, Write Fuse bits and Write Lock bits
commands.
2. t
WLRH_CE
is valid for the Chip Erase command.
24.9 Serial Downloading
Both the Flash and EEPROM memory arrays can be programmed using the serial SPI bus while
RESET is pulled to GND. The serial interface consists of pins SCK, MOSI (input) and MISO (out-
put). After RESET is set low, the Programming Enable instruction needs to be executed first
before program/erase operations can be executed. NOTE, in
Table 24-14 on page 296 , the pin
mapping for SPI programming is listed. Not all parts use the SPI pins dedicated for the internal
SPI interface.
Figure 24-10. Serial Programming and Verify (1)
Notes: 1. If the device is clocked by the internal Oscillator, it is no need to connect a clock source to the
XTAL1 pin.
2. V
CC
- 0.3V < AVCC < V
CC
+ 0.3V, however, AVCC should always be within 1.8 - 5.5V
When programming the EEPROM, an auto-erase cycle is built into the self-timed programming
operation (in the Serial mode ONLY) and there is no need to first execute the Chip Erase
instruction. The Chip Erase operation turns the content of every memory location in both the
Program and EEPROM arrays into 0xFF.
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
24.9.1 Serial Programming Algorithm
When writing serial data to the ATmega32/64/M1/C1, data is clocked on the rising edge of SCK.
t
BVDV
BS1 Valid to DATA valid 0 250 ns
t
OLDV
OE Low to DATA Valid 250 ns
t
OHDZ
OE High to DATA Tri-stated 250 ns
Table 24-15. Parallel Programming Characteristics, V
CC
= 5V ± 10% (Continued)
Symbol Parameter Min Typ Max Units
VCC
GND
XTAL1
SCK_A
MISO_A
MOSI_A
RESET
+1.8 - 5.5V
AVCC
+1.8 - 5.5V (2)