- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄368731 > 16F628 (Microchip Technology Inc.) CAT 5E CROSSOVER PATCH CORD CABLE BLUE 1 FT PDF資料下載
參數(shù)資料
| 型號： | 16F628 |
| 廠商： | Microchip Technology Inc. |
| 英文描述： | CAT 5E CROSSOVER PATCH CORD CABLE BLUE 1 FT |
| 中文描述： | 基于閃存的8位CMOS微控制器 |
| 文件頁數(shù)： | 46/168頁 |
| 文件大小： | 3760K |
| 代理商： | 16F628 |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁第32頁第33頁第34頁第35頁第36頁第37頁第38頁第39頁第40頁第41頁第42頁第43頁第44頁第45頁當(dāng)前第46頁第47頁第48頁第49頁第50頁第51頁第52頁第53頁第54頁第55頁第56頁第57頁第58頁第59頁第60頁第61頁第62頁第63頁第64頁第65頁第66頁第67頁第68頁第69頁第70頁第71頁第72頁第73頁第74頁第75頁第76頁第77頁第78頁第79頁第80頁第81頁第82頁第83頁第84頁第85頁第86頁第87頁第88頁第89頁第90頁第91頁第92頁第93頁第94頁第95頁第96頁第97頁第98頁第99頁第100頁第101頁第102頁第103頁第104頁第105頁第106頁第107頁第108頁第109頁第110頁第111頁第112頁第113頁第114頁第115頁第116頁第117頁第118頁第119頁第120頁第121頁第122頁第123頁第124頁第125頁第126頁第127頁第128頁第129頁第130頁第131頁第132頁第133頁第134頁第135頁第136頁第137頁第138頁第139頁第140頁第141頁第142頁第143頁第144頁第145頁第146頁第147頁第148頁第149頁第150頁第151頁第152頁第153頁第154頁第155頁第156頁第157頁第158頁第159頁第160頁第161頁第162頁第163頁第164頁第165頁第166頁第167頁第168頁
PIC16F627A/628A/648A
DS40044A-page 44
Preliminary
2002 Microchip Technology Inc.
5.3
I/O Programming Considerations
5.3.1
BI-DIRECTIONAL I/O PORTS
Any instruction that writes, operates internally as a read
followed by a write operation. The
BCF
and
BSF
instruc-
tions, for example, read the register into the CPU, exe-
cute 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 bi-directional I/O pin
(e.g., bit0) and 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 bit0 is switched into Output mode later on, the content
of the data latch may now be unknown.
Reading a 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
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-
16). Therefore, care must be exercised if a write fol-
lowed 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 previ-
ous state of that pin may be read into the CPU rather
than the new state. When in doubt, it is better to sepa-
rate these instructions with a
NOP
or another instruction
not accessing this I/O port.
FIGURE 5-16:
SUCCESSIVE I/O OPERATION
;Initial PORT settings:PORTB<7:4> Inputs
;
;PORTB<7:6> have external pull-up and are
;not connected to other circuitry
;
;
PORTB<3:0> Outputs
PORT latchPORT Pins
---------- ----------
;
;01pp pppp 11pp pppp
;
;10pp pppp 11pp pppp
;10pp pppp 10pp pppp
BCF STATUS, RP0
BCF PORTB, 7
BSF STATUS, RP0
BCF TRISB, 7
BCF TRISB, 6
;
;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).
Q1
Q2 Q3 Q4
PC
Instruction
fetched
Q1
Q2 Q3 Q4
Q1
Q2 Q3 Q4 Q1
Q2 Q3 Q4
PC + 1
PC
PC + 2
NOP
PC + 3
NOP
MOVWF
PORTB
Write to PORTB
MOVF
PORTB, W
Read to PORTB
T
PD
Execute
MOVWF
PORTB
Execute
MOVF
PORTB, W
Port pin
sampled here
Execute
NOP
Note
1:
2:
This example shows write to PORTB followed by a read from PORTB.
Data setup time = (0.25 T
CY
- T
PD
) where T
CY
= instruction cycle and T
PD
= propagation delay of Q1 cycle to output valid.
Therefore, at higher clock frequencies, a write followed by a read may be problematic.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| 16M0 | PC SERIAL MODEM CBL 50 FT |
| 16M0B | APPLE IIC CABLE TO IWRTR MODEM |
| 16M0BC | KEYBD.EXT. MINI DIN 4 MM 6 FT |
| 16M0BS | KEYBD.EXT. MINI DIN 4 MM 10 FT |
| 16M0D | MINI DIN 8, MALE-MALE 10 FT. |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 16F630 | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:14-Pin FLASH-Based 8-Bit CMOS Microcontrollers |
| 16F684-I | 制造商:Microchip Technology Inc 功能描述: |
| 16F6H | 制造商:EDAL 制造商全稱:EDAL 功能描述:Silicon High Voltage Assembly |
| 16F6H1 | 制造商:EDAL 制造商全稱:EDAL 功能描述:Silicon High Voltage Assembly |
| 16F7674 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:SMD TWEEZER HEAD |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。