PIC16F874A-E/L Microchip Technology, PIC16F874A-E/L Datasheet - Page 155
![IC,MICROCONTROLLER,8-BIT,PIC CPU,CMOS,LDCC,44PIN,PLASTIC](/photos/6/63/66325/150-44-plcc_sml.jpg)
PIC16F874A-E/L
Manufacturer Part Number
PIC16F874A-E/L
Description
IC,MICROCONTROLLER,8-BIT,PIC CPU,CMOS,LDCC,44PIN,PLASTIC
Manufacturer
Microchip Technology
Series
PIC® 16Fr
Datasheets
1.PIC16F616T-ISL.pdf
(8 pages)
2.PIC16F688T-ISL.pdf
(688 pages)
3.PIC16C770-ISO.pdf
(8 pages)
4.PIC16F873A-ISO.pdf
(234 pages)
5.PIC16F873A-ISO.pdf
(6 pages)
6.PIC16F873A-ISO.pdf
(4 pages)
7.PIC16F873A-ISO.pdf
(6 pages)
8.PIC16F873A-ISO.pdf
(4 pages)
9.PIC16F873A-ISO.pdf
(22 pages)
Specifications of PIC16F874A-E/L
Rohs Compliant
YES
Core Processor
PIC
Core Size
8-Bit
Speed
20MHz
Connectivity
I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
33
Program Memory Size
7KB (4K x 14)
Program Memory Type
FLASH
Eeprom Size
128 x 8
Ram Size
192 x 8
Voltage - Supply (vcc/vdd)
4 V ~ 5.5 V
Data Converters
A/D 8x10b
Oscillator Type
External
Operating Temperature
-40°C ~ 125°C
Package / Case
44-PLCC
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
For Use With
DVA16XL441 - ADAPTER DEVICE ICE 44PLCC309-1040 - ADAPTER 44-PLCC ZIF TO 40-DIP309-1039 - ADAPTER 44-PLCC TO 40-DIP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
PIC16F874A-E/L
Manufacturer:
Microchip Technology
Quantity:
10 000
- PIC16F616T-ISL PDF datasheet
- PIC16F688T-ISL PDF datasheet #2
- PIC16C770-ISO PDF datasheet #3
- PIC16F873A-ISO PDF datasheet #4
- PIC16F873A-ISO PDF datasheet #5
- PIC16F873A-ISO PDF datasheet #6
- PIC16F873A-ISO PDF datasheet #7
- PIC16F873A-ISO PDF datasheet #8
- PIC16F873A-ISO PDF datasheet #9
- Current page: 155 of 688
- Download datasheet (3Mb)
9.10.2
1997 Microchip Technology Inc.
Note:
PIC16CXXX
Successive Operations on an I/O Port
This is not a capacitor to ground, but the effective capac-
itive loading on the trace.
I/O
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
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 a NOP or another instruction not accessing this I/O
port.
Figure 9-12: Successive I/O Operation
Figure 9-13
becomes larger, the rise/fall time of the I/O pin increases. As the device frequency increases or
the effective capacitance increases, the possibility of this subsequent PORTx read-modify-write
instruction issue increases. This effective capacitance includes the effects of the board traces.
The best way to address this is to add an series resistor at the I/O pin. This resistor allows the
I/O pin to get to the desired level before the next instruction.
The use of NOP instructions between the subsequent PORTx read-modify-write instructions, is a
lower cost solution, but has the issue that the number of NOP instructions is dependent on the
effective capacitance C and the frequency of the device.
Figure 9-13: I/O Connection Issues
This example shows a write to PORTB followed by a read from PORTB.
Instruction
Instruction
Note:
RB7:RB0
executed
C
fetched
(1)
shows the I/O model which causes this situation. As the effective capacitance (C)
PORTx, PINy
PC
Data setup time = (0.25T
whereT
T
Therefore, at higher clock frequencies, a write followed by a read may be
problematic due to external capacitance.
PD
Q1
MOVWF PORTB
= propagation delay
write to
PORTB
CY
Q2
PC
V
IL
= instruction cycle
Q3 Q4
BSF PORTx, PINy
Q2
MOVF PORTB,W
MOVWF PORTB
Q1
Q3
write to
PORTB
CY
Q2
PC + 1
Section 9. I/O Ports
- T
Q4
Q3 Q4
PD
Read PORTx, PINy as low
)
BSF PORTx, PINz clears the value
to be driven on the PORTx, PINy pin.
Q1
T
Q1
MOVF PORTB,W
PD
BSF PORTx, PINz
Port pin
sampled here
Q2
NOP
PC + 2
Q2
Q3 Q4
(Figure
Q3
9-12). Therefore, care
Q1
DS31009A-page 9-15
Q4
Q2
PC + 3
NOP
NOP
Q3 Q4
Q1
9
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