279
AT90PWM216/316 [DATASHEET]
7710H–AVR–07/2013
Notes:
1.
tWLRH is valid for the Write Flash, Write EEPROM, Write Fuse bits and Write Lock bits commands.
2.
tWLRH_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 (output). After RESET is set low, the
Programming Enable instruction needs to be executed first before program/erase operations can be executed.
dedicated for the internal SPI interface.
Figure 24-10. Serial Programming and Veri
fy 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. VCC - 0.3V < AVCC < VCC + 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 fck >= 12 MHz
High: > 2 CPU clock cycles for f
ck < 12 MHz, 3 CPU clock cycles for fck >= 12 MHz
24.9.1
Serial Programming Algorithm
When writing serial data to the AT90PWM216/316, data is clocked on the rising edge of SCK.
When reading data from the AT90PWM216/316, data is clocked on the falling edge of SCK. See
Figure 24-11 for
timing details.
To program and verify the AT90PWM216/316 in the serial programming mode, the following sequence is recom-
mended (See four byte instruction formats in
Table 24-16):
1.
Power-up sequence:
Apply power between V
CC and GND while RESET and SCK are set to “0”. In some systems, the program-
mer 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 serial programming by sending the Programming Enable serial instruc-
tion to pin MOSI.
VCC
GND
XTAL1
SCK_A
MISO_A
MOSI_A
RESET
+1.8 - 5.5V
AVCC
+1.8 - 5.5V
(2)