参数资料
型号: MC68HC05T7B
厂商: MOTOROLA INC
元件分类: 微控制器/微处理器
英文描述: 8-BIT, MROM, 2.1 MHz, MICROCONTROLLER, PDIP56
封装: SDIP-56
文件页数: 99/109页
文件大小: 9008K
代理商: MC68HC05T7B
Parallel I/O Ports
Port B
MC68HC705KJ1MC68HRC705KJ1MC68HLC705KJ1 — Rev. 3.0
Technical Data
MOTOROLA
Parallel I/O Ports
89
7.4.2 Data Direction Register B
Data direction register B determines whether each port B pin is an input
or an output.
DDRB[3:2] — Data Direction Register B Bits
These read/write bits control port B data direction. Reset clears
DDRB[3:2], 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 7-8 shows the I/O logic of port B.
Address:
$0005
Bit 7
6
54321
Bit 0
Read:
0
See Notes
DDRB3
DDRB2
See Note
Write:
Reset:
00
000000
= Unimplemented
Note:
DDRB5, DDRB4, DDRB1, and DDRB0 should be configured as inputs at all times. These
bits are available for read/write but are not available externally. Configuring them as inputs
will ensure that the pulldown devices are enabled, thus properly terminating them.
Figure 7-7. Data Direction Register B (DDRB)
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