76
4317I–AVR–01/08
AT90PWM2/3/2B/3B
XCK, USART External clock. The Data Direction Register (DDD0) controls whether the clock is
output (DDD0 set) or input (DDD0 cleared). The XCK0 pin is active only when the USART oper-
ates in Synchronous mode.
SS_A: Slave Port Select input. When the SPI is enabled as a slave, this pin is configured as an
input regardless of the setting of DDD0. As a slave, the SPI is activated when this pin is driven
low. When the SPI is enabled as a master, the data direction of this pin is controlled by DDD0.
When the pin is forced to be an input, the pull-up can still be controlled by the PORTD0 bit.
relates the alternate functions of Port D to the overriding signals
shown in
Table 11-10. Overriding Signals for Alternate Functions PD7..PD4
Signal Name
PD7/
ACMP0
PD6/ADC3/
ACMPM/INT0
PD5/ADC2/
ACMP2
PD4/ADC1/RXD/
ICP1A/SCK_A
PUOE
0
0
0
RXEN + SPE •
MSTR • SPIPS
PUOV
0
0
0
PD4 •
PUD
DDOE
0
0
0
RXEN + SPE •
MSTR • SPIPS
DDOV
0
0
0
0
PVOE
0
0
0
SPE • MSTR •
SPIPS
PVOV
0
0
0
–
DIEOE
ACMP0D
ADC3D + In0en
ADC2D
ADC1D
DIEOV
0
In0en
0
0
DI
–
INT0
ICP1A
AIO
ACOMP0
ADC3
ACMPM
ADC2
ACOMP2
ADC1