70
7679H–CAN–08/08
AT90CAN32/64/128
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.
Note:
1. For the assembly program, two temporary registers are used to minimize the time from pull-
ups are set on pins 0, 1, 6, and 7, until the direction bits are correctly set, defining bit 2 and 3
as low and redefining bits 0 and 1 as strong high drivers.
9.2.5
Digital Input Enable and Sleep Modes
As shown in
, the digital input signal can be clamped to ground at the input of the
schmitt-trigger. The signal denoted SLEEP in the figure, is set by the MCU Sleep Controller in
Power-down mode, Power-save mode, and Standby mode to avoid high power consumption if
some input signals are left floating, or have an analog signal level close to V
CC
/2.
SLEEP is overridden for port pins enabled as external interrupt pins. If the external interrupt
request is not enabled, SLEEP is active also for these pins. SLEEP is also overridden by various
other alternate functions as described in
“Alternate Port Functions” on page 71
If a logic high level (“one”) is present on an Asynchronous External Interrupt pin configured as
“Interrupt on Rising Edge, Falling Edge, or Any Logic Change on Pin” while the external interrupt
is not
enabled, the corresponding External Interrupt Flag will be set when resuming from the
Assembly Code Example
...
;
Define pull-ups and set outputs high
;
Define directions for port pins
ldi
r16, (1<<PB7)|(1<<PB6)|(1<<PB1)|(1<<PB0)
ldi
r17, (1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0)
out
PORTB, r16
out
DDRB, r17
;
Insert nop for synchronization
nop
;
Read port pins
in
r16, PINB
...
C Code Example
unsigned char
i;
...
/*
Define pull-ups and set outputs high
*/
/*
Define directions for port pins
*/
PORTB = (1<<PB7)|(1<<PB6)|(1<<PB1)|(1<<PB0);
DDRB = (1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0);
/*
Insert nop for synchronization
*/
_NOP();
/*
Read port pins
*/
i = PINB;
...
