參數(shù)資料
型號(hào)： PIC12F519
廠商： Microchip Technology Inc.
英文描述： 8-Pin, 8-Bit Flash Microcontroller
中文描述： 8引腳，8位閃存微控制器
文件頁(yè)數(shù)： 30/88頁(yè)
文件大?。?/td> 802K
代理商： PIC12F519
PIC12F519
DS41319A-page 28
Preliminary
2007 Microchip Technology Inc.
6.4
I/O Programming Considerations
6.4.1
BIDIRECTIONAL I/O PORTS
Some instructions operate internally as read followed
by write operations. The
BCF
and
BSF
instructions, for
example, read the entire port into the CPU, execute the
bit operation and re-write the result. Caution must be
used when these instructions are applied to a port
where one or more pins are used as input/outputs. For
example, a
BSF
operation on bit 5 of PORTB will cause
all eight bits of PORTB to be read into the CPU, bit 5 to
be set and the PORTB value to be written to the output
latches. If another bit of PORTB is used as a bidirec-
tional I/O pin (say bit 0) 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 rewritten 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 bit 0 is switched into Output mode
later on, the content of the data latch may now be
unknown.
Example 6-1 shows the effect of two sequential
Read-Modify-Write instructions (e.g.,
BCF, BSF
, etc.)
on an I/O port.
A pin actively outputting a high or a low 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 6-1:
READ-MODIFY-WRITE
INSTRUCTIONS ON AN
I/O PORT
6.4.2
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 6-2).
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 allow the pin voltage to
stabilize (load dependent) before the next instruction
causes that file to be read into the CPU. 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 a
NOP
or another instruction not
accessing this I/O port.
FIGURE 6-2:
SUCCESSIVE I/O OPERATION
;Initial PORTB Settings
;PORTB<5:3> Inputs
;PORTB<2:0> Outputs
;
;
;
BCF
PORTB, 5 ;--01 -ppp
BCF
PORTB, 4 ;--10 -ppp
MOVLW
007h;
TRIS
PORTB
;
Note
1:
The user may have expected the pin values to
be ‘
--00 pppp
’. The 2nd
BCF
caused RB5 to
be latched as the pin value (High).
PORTB latch
----------
PORTB pins
----------
--11 pppp
--11 pppp
;--10 -ppp
--11 pppp
PC
PC + 1
PC + 2
PC + 3
Q1 Q2
Q3 Q4
Q1 Q2
Q3 Q4
Q1
Q2 Q3 Q4
Q1 Q2
Q3 Q4
Instruction
Fetched
RB<5:0>
MOVWF
PORTB
NOP
Port pin
sampled here
NOP
MOVF
PORTB
,
W
Instruction
Executed
MOVWF PORTB
(Write to PORTB)
NOP
MOVF PORTB,W
(Read PORTB)
This example shows a write to PORTB
followed by a read from PORTB.
Data setup time = (0.25 T
CY
– T
PD
)
where: T
CY
= instruction cycle.
T
PD
= propagation delay
Therefore, at higher clock frequencies, a
write followed by a read may be problematic.
Port pin
written here
相關(guān)PDF資料
PDF描述
PIC12F609 8-bit PIC㈢ Microcontrollers with High Voltage Support and Fan Control Capabilities
PIC12F615 8-bit PIC㈢ Microcontrollers with High Voltage Support and Fan Control Capabilities
PIC12HV609 8-bit PIC㈢ Microcontrollers with High Voltage Support and Fan Control Capabilities
PIC12HV615 8-Pin Flash-Based, 8-Bit CMOS Microcontrollers
PIC16C505-04 14-Pin, 8-Bit CMOS Microcontroller
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
PIC12F519_08 制造商:MICROCHIP 制造商全稱(chēng):Microchip Technology 功能描述:8-Pin, 8-Bit Flash Microcontrollers
PIC12F519-E/MC 功能描述:8位微控制器 -MCU 15KB Flash Prgrm 64B 8MHz Intrnl Oscilatr 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
PIC12F519-E/MS 功能描述:8位微控制器 -MCU 15KB Flash Prgrm 64B 8MHz Intrnl Oscilatr 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
PIC12F519-E/P 功能描述:8位微控制器 -MCU 15KB Flash Prgrm 64B 8MHz Intrnl Oscilatr 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
PIC12F519-E/SN 功能描述:8位微控制器 -MCU 15KB Flash Prgrm 64B 8MHz Intrnl Oscilatr 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(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫(xiě)一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。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(gòu)。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(gòu)

我的聯(lián)系方式

*
*
*