AT90PWM2B-16SE ATMEL [ATMEL Corporation], AT90PWM2B-16SE Datasheet - Page 64

• Manufacturer Part Number: AT90PWM2B-16SE
• Description: 8-bit Microcontroller with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

64
AT90PWM2/3/2B/3B
Figure 11-3. Synchronization when Reading an Externally Applied Pin value
Consider the clock period starting shortly after the first falling edge of the system clock. The latch
is closed when the clock is low, and goes transparent when the clock is high, as indicated by the
shaded region of the “SYNC LATCH” signal. The signal value is latched when the system clock
goes low. It is clocked into the PINxn Register at the succeeding positive clock edge. As indi-
cated by the two arrows t
between ½ and 1½ system clock period depending upon the time of assertion.
When reading back a software assigned pin value, a nop instruction must be inserted as indi-
cated in
the clock. In this case, the delay t
Figure 11-4. Synchronization when Reading a Software Assigned Pin Value
The following code example shows how to set port B pins 0 and 1 high, 2 and 3 low, and define
the port pins from 4 to 7 as input with pull-ups assigned to port pins 6 and 7. The resulting pin
Figure
INSTRUCTIONS
INSTRUCTIONS
SYSTEM CLK
SYSTEM CLK
SYNC LATCH
SYNC LATCH
11-4. The out instruction sets the “SYNC LATCH” signal at the positive edge of
PINxn
PINxn
r17
r16
r17
pd,max
and t
pd
through the synchronizer is 1 system clock period.
out PORTx, r16
pd,min
XXX
, a single signal transition on the pin will be delayed
t
pd, max
0x00
0x00
XXX
nop
t
pd
t
0xFF
pd, min
in r17, PINx
in r17, PINx
4317J–AVR–08/10
0xFF
0xFF