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| 型號： | PIC12F519-I/SN |
| 廠商： | Microchip Technology |
| 文件頁數(shù)： | 26/96頁 |
| 文件大小： | 0K |
| 描述： | IC PIC MCU FLASH 1KX12 8SOIC |
| 產(chǎn)品培訓模塊： | Asynchronous Stimulus 8-bit PIC® Microcontroller Portfolio |
| 標準包裝： | 100 |
| 系列： | PIC® 12F |
| 核心處理器： | PIC |
| 芯體尺寸： | 8-位 |
| 速度： | 8MHz |
| 外圍設(shè)備： | POR，WDT |
| 輸入/輸出數(shù)： | 5 |
| 程序存儲器容量： | 1.5KB（1K x 12） |
| 程序存儲器類型： | 閃存 |
| RAM 容量： | 41 x 8 |
| 電壓 - 電源 (Vcc/Vdd)： | 2 V ~ 5.5 V |
| 振蕩器型： | 內(nèi)部 |
| 工作溫度： | -40°C ~ 85°C |
| 封裝/外殼： | 8-SOIC（0.154"，3.90mm 寬） |
| 包裝： | 管件 |
| 產(chǎn)品目錄頁面： | 637 (CN2011-ZH PDF) |
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PIC12F519
DS41319B-page 30
2008 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 GPIO will cause
all eight bits of GPIO to be read into the CPU, bit 5 to
be set and the GPIO value to be written to the output
latches. If another bit of GPIO is used as a bidirectional
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 6-6).
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 6-6:
SUCCESSIVE I/O OPERATION
;Initial GPIO Settings
;GPIO<5:3> Inputs
;GPIO<2:0> Outputs
;
GPIO latch
GPIO pins
;
----------
BCF
GPIO, 5
;--01 -ppp
--11 pppp
BCF
GPIO, 4
;--10 -ppp
--11 pppp
MOVLW
007h;
TRIS
GPIO
;--10 -ppp
--11 pppp
;
Note
1:
The user may have expected the pin values to
be ‘--00 pppp’. The 2nd BCF caused GP5 to
be latched as the pin value (High).
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
GP<5:0>
MOVWF GPIO
NOP
Port pin
sampled here
NOP
MOVF GPIO
, W
Instruction
Executed
MOVWF GPIO
(Write to GPIO)
NOP
MOVF PORTB,W
This example shows a write to GPIO followed
by a read from GPIO.
Data setup time = (0.25 TCY – TPD)
where: TCY = instruction cycle.
TPD = propagation delay
Therefore, at higher clock frequencies, a
write followed by a read may be problematic.
(Read PORTB)
Port pin
written here
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相關(guān)代理商/技術(shù)參數(shù) |
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| PIC12F519T-E/MC | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:8-Pin, 8-Bit Flash Microcontroller |
| PIC12F519T-E/MS | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:8-Pin, 8-Bit Flash Microcontroller |
| PIC12F519T-E/P | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:8-Pin, 8-Bit Flash Microcontroller |
| PIC12F519T-E/SN | 制造商:Microchip Technology Inc 功能描述:8-PIN, 1.5KB FLASH PROGRAM, 64 - Tape and Reel |
| PIC12F519T-I/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 最大時鐘頻率:50 MHz 程序存儲器大小: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 安裝風格:SMD/SMT |
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