ATA5771-DK1 Atmel, ATA5771-DK1 Datasheet - Page 62

• Manufacturer Part Number: ATA5771-DK1
• Description: BOARD XMITTER FOR ATA5771 868MHZ
• Manufacturer: Atmel
• Type: Transmitterr

Specifications of ATA5771-DK1

• Frequency: 868MHz
• Maximum Frequency: 868 MHz
• Supply Voltage (max): 4 V
• Supply Voltage (min): 2 V
• Supply Current: 8.5 mA
• Product: RF Development Tools
• For Use With/related Products: ATA5771
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4.14.2.1
4.14.2.2
4.14.2.3
62
Atmel ATA5771/73/74
Configuring the Pin
Toggling the Pin
Switching Between Input and Output
Each port pin consists of three register bits: DDxn, PORTxn, and PINxn. As shown in
4-29 on page
PORTx I/O address, and the PINxn bits at the PINx I/O address.
The DDxn bit in the DDRx Register selects the direction of this pin. If DDxn is written logic one,
Pxn is configured as an output pin. If DDxn is written logic zero, Pxn is configured as an input
pin.
If PORTxn is written logic one when the pin is configured as an input pin, the pull-up resistor is
activated. To switch the pull-up resistor off, PORTxn has to be written logic zero or the pin has
to be configured as an output pin. The port pins are tri-stated when reset condition becomes
active, even if no clocks are running.
If PORTxn is written logic one when the pin is configured as an output pin, the port pin is
driven high (one). If PORTxn is written logic zero when the pin is configured as an output pin,
the port pin is driven low (zero).
Writing a logic one to PINxn toggles the value of PORTxn, independent on the value of
DDRxn. Note that the SBI instruction can be used to toggle one single bit in a port.
When switching between tri-state ({DDxn, PORTxn} = 0b00) and output high ({DDxn,
PORTxn} = 0b11), an intermediate state with either pull-up enabled {DDxn, PORTxn} = 0b01)
or output low ({DDxn, PORTxn} = 0b10) must occur. Normally, the pull-up enabled state is fully
acceptable, as a high-impedant environment will not notice the difference between a strong
high driver and a pull-up. If this is not the case, the PUD bit in the MCUCR Register can be set
to disable all pull-ups in all ports.
Switching between input with pull-up and output low generates the same problem. The user
must use either the tri-state ({DDxn, PORTxn} = 0b00) or the output high state
({DDxn, PORTxn} = 0b10) as an intermediate step.
Table 4-21
Table 4-21.
DDxn
0
0
0
1
1
PORTxn
summarizes the control signals for the pin value.
74, the DDxn bits are accessed at the DDRx I/O address, the PORTxn bits at the
0
1
1
0
1
Port Pin Configurations
(in MCUCR)
PUD
X
0
1
X
X
Output
Output
Input
Input
Input
I/O
Pull-up
Yes
No
No
No
No
Comment
Tri-state (Hi-Z)
Pxn will source current if ext. pulled low.
Tri-state (Hi-Z)
Output Low (Sink)
Output High (Source)
9137E–RKE–12/10
Table