Datasheet

252
7734Q–AVR–02/12
AT90PWM81/161
21.4 Calibration Byte
The AT90PWM81/161 has a byte calibration value for the internal RC Oscillator. This byte
resides in the byte of address 0x003 in the signature address space. During reset, this byte is
automatically written into the OSCCAL Register to ensure correct frequency of the calibrated RC
Oscillator.
21.5 Parallel Programming Parameters, Pin Mapping, and Commands
This section describes how to parallel program and verify Flash Program memory, EEPROM
Data memory, Memory Lock bits, and Fuse bits in the AT90PWM81/161. Pulses are assumed to
be at least 250ns unless otherwise stated.
21.5.1 Signal Names
In this section, some pins of the AT90PWM81/161 are referenced by signal names describing
their functionality during parallel programming, see Figure 21-1 and Table 21-8. Pins not
described in Table 21-8 are referenced by pin names.
The XA1/XA0 pins determine the action executed when the XTAL1 pin is given a positive pulse.
The bit coding is shown in Table 21-10 on page 253.
When pulsing WR
or OE, the command loaded determines the action executed. The different
Commands are shown in Table 21-11 on page 253.
Figure 21-1. Parallel programming.
Table 21-8. Pin name mapping.
Signal name in
programming mode Pin name I/O Function
RDY/BSY
AREF O
0: Device is busy programming,
1: Device is ready for new command
OE PD2 I Output enable (active low)
WR
PD1 I Write pulse (active low)
XA0 PD5 I XTAL Action Bit 0
VCC
GND
XTAL1/PE1
XA0
RDY/BSY
OE
RESET/PE0
+5V
AVCC
+5V
AREF
+12V
PE 2
PD6
PD5
PD1
PD2
WR
XA1/BS2
PAGEL/BS1
DATA
PB[7:0]