參數(shù)資料
型號(hào)： PIC16C621
廠商： Microchip Technology Inc.
英文描述： EPROM-Based 8-Bit CMOS Microcontroller(每個(gè)I/O口有25mA驅(qū)動(dòng)/吸收電流,可編程參考電壓，微控制器)
中文描述： 存儲(chǔ)器為基礎(chǔ)的8位CMOS微控制器（每個(gè)的I / O口有25毫安驅(qū)動(dòng)/吸收電流，可編程參考電壓，微控制器）
文件頁數(shù)： 30/112頁
文件大?。?/td> 1205K
代理商： PIC16C621
PIC16C62X(A)
DS30235F-page 30
Preliminary
1997 Microchip Technology Inc.
5.3
I/O Programming Considerations
5.3.1
BI-DIRECTIONAL I/O PORTS
Any instruction which writes, operates internally as a
read followed by a write operation. The
BCF
and
BSF
instructions, for example, read the register into the
CPU, execute the bit operation and write the result back
to the register. Caution must be used when these
instructions are applied to a port with both inputs and
outputs defined. For example, a
BSF
operation on bit5
of PORTB will cause all eight bits of PORTB to be read
into the CPU. Then the
BSF
operation takes place on
bit5 and PORTB is written to the output latches. If
another bit of PORTB is used as a bidirectional I/O pin
(e.g., bit0) and it is defined as an input at this time, the
input signal present on the pin itself would be read into
the CPU and re-written to the data latch of this
particular pin, overwriting the previous content. As long
as the pin stays in the input mode, no problem occurs.
However, if bit0 is switched into output mode later on,
the content of the data latch may now be unknown.
Reading the port register, reads the values of the port
pins. Writing to the port register writes the value to the
port latch. When using read modify write instructions
(ex.
BCF, BSF
, etc.) on a port, the value of the port pins
is read, the desired operation is done to this value, and
this value is then written to the port latch.
Example 5-2 shows the effect of two sequential
read-modify-write instructions (ex.,
BCF, BSF
, etc.) on
an I/O port.
A pin actively outputting a Low or High should not be
driven from external devices at the same time in order
to change the level on this pin (“wired-or”, “wired-and”).
The resulting high output currents may damage
the chip.
EXAMPLE 5-2:
READ-MODIFY-WRITE
INSTRUCTIONS ON AN
I/O PORT
PORTB<7:4> Inputs
5.3.2
SUCCESSIVE OPERATIONS ON I/O PORTS
The actual write to an I/O port happens at the end of an
instruction cycle, whereas for reading, the data must be
valid at the beginning of the instruction cycle
(Figure 5-7). Therefore, care must be exercised if a
write followed by a read operation is carried out on the
same I/O port. The sequence of instructions should be
such to allow the pin voltage to stabilize (load
dependent) before the next instruction which causes
that file to be read into the CPU is executed. Otherwise,
the previous state of that pin may be read into the CPU
rather than the new state. When in doubt, it is better to
separate these instructions with an NOP or another
instruction not accessing this I/O port.
;
;
;
;
;
;
;
;
Initial PORT settings:
PORTB<3:0> Outputs
PORTB<7:6> have external pull-up and are not
connected to other circuitry
PORT latch PORT pins
---------- ----------
BCF PORTB, 7
BCF PORTB, 6
BSF STATUS,RP0
BCF TRISB, 7
BCF TRISB, 6
; 01pp pppp
; 10pp pppp
;
; 10pp pppp
; 10pp pppp
11pp pppp
11pp pppp
11pp pppp
10pp pppp
;
; Note that the user may have expected the pin
; values to be 00pp pppp. The 2nd BCF caused
; RB7 to be latched as the pin value (High).
FIGURE 5-7:
SUCCESSIVE I/O OPERATION
Note:
This example shows write to PORTB
followed by a read from PORTB.
Note that:
data setup time = (0.25 T
- T
)
where T
CY
= instruction cycle and
T
= propagation delay of Q1 cycle
to output valid.
Therefore, at higher clock frequencies,
a write followed by a read may be
problematic.
Q1 Q2 Q3 Q4
Q1 Q2 Q3 Q4
Q1 Q2
Q3 Q4
Q1 Q2
Q3 Q4
Port pin
sampled here
PC
PC + 1
PC + 2
PC + 3
NOP
NOP
MOVF PORTB, W
Read PORTB
MOVWF PORTB
Write to
PORTB
PC
Instruction
fetched
T
PD
Execute
MOVWF
PORTB
Execute
MOVF
PORTB, W
Execute
NOP
RB7:RB0
相關(guān)PDF資料
PDF描述
pic16c621a EPROM-Based 8-Bit CMOS Microcontroller(8位CMOS微控制器)
PIC16C622 EPROM-Based 8-Bit CMOS Microcontroller(每個(gè)I/O口有25mA驅(qū)動(dòng)/吸收電流,可編程VREF,2.5V的微控制器)
pic16c622a EPROM-Based 8-Bit CMOS Microcontroller(8位CMOS微控制器)
PIC16C62B 28-Pin 8-Bit CMOS Microcontrollers(28引腳，8位CMOS微控制器)
PIC16C63A 8-Bit CMOS Microcontrollers with A/D Converter(8位、帶A/D轉(zhuǎn)換器的CMOS微控制器)
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
PIC16C621/JW 功能描述:8位微控制器 -MCU 1.75KB 80 RAM 13 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時(shí)鐘頻率:50 MHz 程序存儲(chǔ)器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT
PIC16C621-04/P 功能描述:8位微控制器 -MCU 1.75KB 80 RAM 13 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時(shí)鐘頻率:50 MHz 程序存儲(chǔ)器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT
PIC16C621-04/P 制造商:Microchip Technology Inc 功能描述:IC 8BIT CMOS MCU 16C621 DIP18
PIC16C621-04/SO 功能描述:8位微控制器 -MCU 1.75KB 80 RAM 13 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時(shí)鐘頻率:50 MHz 程序存儲(chǔ)器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT
PIC16C621-04/SS 功能描述:8位微控制器 -MCU 1.75KB 80 RAM 13 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時(shí)鐘頻率:50 MHz 程序存儲(chǔ)器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。

采購需求

(若只采購一條型號(hào)，填寫一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購

我的聯(lián)系方式

*
*
*