參數(shù)資料
型號: MC68HC08QT2CDWE
廠商: FREESCALE SEMICONDUCTOR INC
元件分類: 微控制器/微處理器
英文描述: 8-BIT, FLASH, 8 MHz, MICROCONTROLLER, PDSO8
封裝: LEAD FREE, EIAJ, SOIC-8
文件頁數(shù): 4/176頁
文件大?。?/td> 1124K
代理商: MC68HC08QT2CDWE
Port B
MC68HC08QY/QT Family Data Sheet, Rev. 2
Freescale Semiconductor
101
12.4.2 Data Direction Register B
Data direction register B (DDRB) determines whether each port B pin is an input or an output. Writing a 1
to a DDRB bit enables the output buffer for the corresponding port B pin; a 0 disables the output buffer.
DDRB[7:0] — Data Direction Register B Bits
These read/write bits control port B data direction. Reset clears DDRB[7:0], configuring all port B pins
as inputs.
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
NOTE
Avoid glitches on port B pins by writing to the port B data register before
changing data direction register B bits from 0 to 1. Figure 12-7 shows the
port B I/O logic.
Figure 12-7. Port B I/O Circuit
When DDRBx is a 1, reading PTB reads the PTBx data latch. When DDRBx is a 0, reading PTB reads
the logic level on the PTBx pin. The data latch can always be written, regardless of the state of its data
direction bit.
Bit 7
654
32
1
Bit 0
Read:
DDRB7
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
Write:
Reset:
0
000
00
Figure 12-6. Data Direction Register B (DDRB)
READ DDRB
WRITE DDRB
RESET
WRITE PTB
READ PTB
PTBx
DDRBx
PTBx
IN
TERNAL
DATA
BUS
PULLUP
PTBPUEx
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