參數(shù)資料
型號(hào): R5F3650NNFB
元件分類: 微控制器/微處理器
英文描述: MICROCONTROLLER, PQFP100
封裝: 14 X 14 MM, 0.50 MM PITCH, LQFP-100
文件頁(yè)數(shù): 46/81頁(yè)
文件大小: 879K
代理商: R5F3650NNFB
64
4317K–AVR–03/2013
AT90PWM2/3/2B/3B
11.2.2
Toggling the Pin
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.
11.2.3
Switching Between Input and Output
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 accept-
able, 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}
= 0b11) as an intermediate step.
Table 11-1 summarizes the control signals for the pin value.
11.2.4
Reading the Pin Value
Independent of the setting of Data Direction bit DDxn, the port pin can be read through the
PINxn Register bit. As shown in Figure 11-2, the PINxn Register bit and the preceding latch con-
stitute a synchronizer. This is needed to avoid metastability if the physical pin changes value
near the edge of the internal clock, but it also introduces a delay. Figure 11-3 shows a timing dia-
gram of the synchronization when reading an externally applied pin value. The maximum and
minimum propagation delays are denoted t
pd,max and tpd,min respectively.
Table 11-1.
Port Pin Configurations
DDxn
PORTxn
PUD
(in MCUCR)
I/O
Pull-up
Comment
0
X
Input
No
Default configuration after Reset.
Tri-state (Hi-Z)
0
1
0
Input
Yes
Pxn will source current if ext. pulled low.
0
1
Input
No
Tri-state (Hi-Z)
1
0
X
Output
No
Output Low (Sink)
1
X
Output
No
Output High (Source)
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