Self study notes -- use of 74h573

One 、74h573 Pin distribution diagram and truth table of

 

 

Two 、 The meaning of each letter

OE： The three states allow the control end , Also called output enable and output allow , Generally, the low level is effective .（ Normally OE It is marked with a horizontal line ）

D and Q： They are input and output respectively .

LE: Latch permissive end .H： High level .L： Low level .X： Any level .Z： Out of control .

3、 ... and 、 Specific principles and methods of use

        As can be seen from the truth table , When 74H573 Of OE No matter when the terminal is high LE And the level of the input terminal , The output is uncontrollable , So in most cases, it will be OE Terminal grounding , It can also be connected to low level , determine OE After the status is determined LE, It can be seen from the table that LE Low power level ,Q The end data status will remain LE Before the terminal changes to low level Q End data status .

          So in use , take OE Grounding , take LE Connect to a certain pin of the MCU , then D End and a certain group of single-chip computers I/O Mouth to mouth .

Four 、 The purpose of using the latch on the learning version （ in the light of TX-1C For the learning version ）

        The LED is connected to the single chip microcomputer through a latch P1 mouth , And on the edition A/D The data output end of the chip is also connected to the MCU P1 mouth , When we are doing A/D During the experiment ,A/D The data at the data output end of the chip will change in real time , If no latch is added , Then the light-emitting diode will keep flashing , So we're doing A/D The latch can be closed during the experiment （ to LE A low level ）

Be careful ： When writing the flow lamp program , Why didn't you write a program to open the latch , Because in 51 As soon as the single chip microcomputer is powered on , All uncontrolled I/O All ports are set to high level by default .