AT90S4414/8515
77
Serial Downloading
Both the Program and Data memory arrays can be programmed using the SPI bus while RESET is pulled to GND. The
serial interface consists of pins SCK, MOSI (input) and MISO (output), see Figure 64. After RESET is set low, the Program-
ming Enable instruction needs to be executed first before program/erase instructions can be executed.
Figure 64. Serial Programming and Verify
For the EEPROM, an auto-erase cycle is provided within the self-timed write instruction and there is no need to first exe-
cute the Chip Erase instruction. The Chip Erase instruction turns the content of every memory location in both the Program
and EEPROM arrays into $FF.
The Program and EEPROM memory arrays have separate address spaces:
$0000 to $07FF/$0FFF (AT90S4414/8515) for Program memory and $0000 to $00FF/$01FF (AT90S4414/8515) for
EEPROM memory.
Either an external clock is supplied at pin XTAL1 or a crystal needs to be connected across pins XTAL1 and XTAL2.The
minimum low and high periods for the serial clock (SCK) input are defined as follows:
Low: > 2 XTAL1 clock cycles
High: > 2 XTAL1 clock cycles
AT90S4414/8515
VCC
+2.7V - 6.0V
PB7(SCK)
PB6(MISO)
PB5(MOSI)
RESET
GND
XTAL1
XTAL2
1 to 8 MHz
CLOCK IN
DATA OUT
INSTR. IN
GND