Rainbow-electronics ATmega64L Bedienungsanleitung PDF herunterladen (Seite 50)

ATmega16(L)

2466B–09/01

ceeding positive clock edge. As indicated by the two arrows t

pd,max

and t

pd,min

, a single

signal transition on the pin will be delayed between ½ and 1-½ system clock period

depending upon the time of assertion.

When reading back a software assigned pin value, a nop instruction must be inserted as

indicated in Figure 25. The out instruction sets the “SYNC LATCH” signal at the positive

edge of the clock. In this case, the delay t

through the synchronizer is 1 system clock

period.

Figure 25. 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 values are read back again, but as previously discussed, a nop instruction

is included to be able to read back the value recently assigned to some of the pins.

nop in r17, PINx

0xFF

0x00

0xFF

out PORTx, r16

SYSTEM CLK

r16

INSTRUCTIONS

SYNC LATCH

PINxn

r17

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Rainbow-electronics ATmega64L Bedienungsanleitung Seite 50