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please explain what U1 does.
pixelbeat

pixelbeat

@copilot please explain what U1 does.
2y

copilot

U1, designated as CD4021BE, is an 8-bit shift register from Texas Instruments. Its primary function within the Nintendo Controller project you're working on is to serialize the state of the buttons pressed on the controller and send this data to the console. Here's a more detailed breakdown of its role and how it operates in this context:
  • Serial Data Transmission: The CD4021BE captures the state of up to eight buttons in parallel and then shifts this data out serially. This allows the Nintendo console to read the state of all buttons using only a single data line, which significantly reduces the wiring complexity and the number of I/O ports required on the console.
  • Button Inputs: The parallel inputs $PI-1$ to $PI-8$ on the CD4021BE are connected to the various buttons on the controller like UP, DOWN, LEFT, RIGHT, A, B, START, and SELECT through resistors. These inputs capture the state of each button when the shift register is latched.
  • Latch Functionality: The P/S $Parallel/Serial Control$ pin is used to switch between loading the parallel inputs into the shift register $latching$ and shifting the data out serially. When P/S is high, the register latches the state of the parallel inputs. When P/S is low, the register shifts out the data serially on the Q7 or SERIAL pin.
  • Clocking: The CLOCK pin is used to shift the serial data out of the shift register. Each pulse on the CLOCK pin shifts the data one bit position, allowing the serial data to be read by the console.
  • Power Supply and Grounding: VDD and VSS pins are connected to the power supply $5V$ and ground, respectively, providing the necessary power for the shift register to operate.
In summary, U1 plays a crucial role in interfacing the NES controller with the console, allowing for a compact and efficient communication of button states through serial data transmission.
2y
1
P7
R1
Resistance
1kΩ
U1
GND
R8
Resistance
1kΩ
R4
Resistance
1kΩ
P1
P6
P4
R10
Resistance
3.6kΩ
R6
Resistance
1kΩ
R2
Resistance
1kΩ
R5
Resistance
1kΩ
VCC
CLOCK
P3
R3
Resistance
1kΩ
R7
Resistance
1kΩ
DATA
P2
P5
R9
Resistance
3.6kΩ
P8
LATCH
RIGHT
A
B
UP
DOWN
SELECT
START
LEFT

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    Assets

    nes_flux_thumb.png

    nes_flux_thumb.png

    nes_flux_thumbThumbnail

    nes_controller_outline.svg

    nes_controller_outline

    nes_outlines.svg

    nes_outlines

    nes_flux.svg

    nes_fluxDefault

    Flux-Logo.svg

    Flux-Logo

    Nintendo Controller

    Nintendo Controller thumbnail
    Original Nintendo Entertainment System (NES) controller. Just like the originals, it uses a CD4021B 8-bit shift register to send serial data of the button state to the console.

    Properties

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    Pricing & Availability

    Distributor

    Qty 1

    LCSC

    $0.50

    Mouser

    $1.25

    Controls