Rainbow Electronics ATmega128RFA1 - Manual (Page 204)

204
8266A-MCU Wireless-12/09
ATmega128RFA1
14.4 Register Description
14.4.1 MCUCR – MCU Control Register
Bit 7 6 5 4 3 2 1 0
$35 ($55) PUD MCUCR
Read/Write RW
Initial Value 0
The MCU Control Register contains control bits of the general Microcontroller Unit
functions.
• Bit 4 – PUD - Pull-up Disable
When this bit is written to one, the I/O ports pull-up resistors are disabled even if the
DDxn and PORTxn Registers are configured to enable the pull-up resistor ({DDxn,
PORTxn} = 2'b01). See section "Ports as General Digital I/O" for more details about this
feature.
14.4.2 DPDS0 – Port Driver Strength Register 0
Bit 7 6 5 4 3 2 1 0
NA ($136) PFDRV1 PFDRV0 PEDRV1 PEDRV0 PDDRV1 PDDRV0 PBDRV1 PBDRV0 DPDS0
Read/Write RW RW RW RW RW RW RW RW
Initial Value 0 0 0 0 0 0 0 0
The output driver strength can be set individually for each digital I/O port. The following
tables show output current levels for a typical supply voltage of DEVDD = 3.3V. Refer to
section "Electrical Characteristics" for details.
• Bit 7:6 – PFDRV1:0 - Driver Strength Port F
Table 14-18 PFDRV Register Bits
Register Bits Value Description
0 2 mA
1 4 mA
2 6 mA
PFDRV1:0
3 8 mA
• Bit 5:4 – PEDRV1:0 - Driver Strength Port E
Table 14-19 PEDRV Register Bits
Register Bits Value Description
0 2 mA
1 4 mA
2 6 mA
PEDRV1:0
3 8 mA
• Bit 3:2 – PDDRV1:0 - Driver Strength Port D