參數(shù)資料
型號: MC68HC08LT8CFGE
廠商: FREESCALE SEMICONDUCTOR INC
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 4 MHz, MICROCONTROLLER, PQFP44
封裝: 10 X 10 MM, 1.40 MM THICKNESS, 0.80 MM PITCH, ROHS COMPLIANT, MS-026BCB, LQFP-44
文件頁數(shù): 6/156頁
文件大小: 1107K
代理商: MC68HC08LT8CFGE
Port D
MC68HC08LT8 Data Sheet, Rev. 1
Freescale Semiconductor
103
9.5.2 Data Direction Register D (DDRD)
Data direction register D determines whether each port D pin is an input or an output. Writing a logic 1 to
a DDRD bit enables the output buffer for the corresponding port D pin; a logic 0 disables the output buffer.
DDRD[7:0] — Data Direction Register D Bits
These read/write bits control port D data direction. Reset clears DDRD[7:0], configuring all port D pins
as inputs.
1 = Corresponding port D pin configured as output
0 = Corresponding port D pin configured as input
NOTE
Avoid glitches on port D pins by writing to the port D data register before
changing data direction register D bits from 0 to 1. Figure 9-14 shows the
port D I/O logic.
Figure 9-14. Port D I/O Circuit
When DDRDx is a logic 1, reading address $0003 reads the PTDx data latch. When DDRDx is a logic 0,
reading address $0003 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 9-5 summarizes the operation of the port D pins.
Address:
$0007
Bit 7
6
54
32
1
Bit 0
Read:
DDRD7
DDRD6
DDRD5
DDRD4
DDRD3
DDRD2
DDRD1
DDRD0
Write:
Reset:
000
00
000
Figure 9-13. Data Direction Register D (DDRD)
Table 9-5. Port D Pin Functions
DDRD
Bit
PTD Bit
I/O Pin Mode
Accesses to DDRD
Accesses to PTD
Read/Write
Read
Write
0
X(1)
1. X = don’t care; except.
Input, Hi-Z(2)
2. Hi-Z = high impedance.
DDRD[7:0]
Pin
PTD[7:0](3)
3. Writing affects data register, but does not affect input.
1
X
Output
DDRD[7:0]
PTD[7:0]
READ DDRD ($0007)
WRITE DDRD ($0007)
RESET
WRITE PTD ($0003)
READ PTD ($0003)
PTDx
DDRDx
PTDx
INTE
RNAL
D
AT
A
B
U
S
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