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how do I connect U1 and U2?
danniell

danniell

@copilot how do I connect U1 and U2?
1y

copilot

To connect U1 and U2, which are both SN74LS148D 8-line-to-3-line priority encoders from Texas Instruments, we should focus on setting up a cascading configuration to manage a larger number of inputs by utilizing the enable and output lines effectively. This setup allows for handling more than 8 inputs by cascading two or more encoders.
The SN74LS148D has an Enable input (EI) and an Enable output (EO) that can be used for cascading purposes. Here's how you can connect U1 and U2 for cascading:
  1. Power Supply Connections:
    • Connect both U1:16 (VCC) and U2:16 (VCC) to the positive supply voltage.
    • Connect both U1:8 (GND) and U2:8 (GND) to the ground.
  2. Cascading Connections for expanding input handling capability:
    • To cascade U1 to U2, connect U1:15 (EO) to U2:5 (EI). This connection ensures that when U1's outputs are not valid (indicating all inputs are high and it is therefore inactive), U2 is enabled.
    • All unused inputs on U1 and U2 should be tied to a logical high state to ensure proper functioning. For instance, if you're not using all input lines, make sure that those unused input pins (1 to 4 on both U1 and U2 for the sake of example) are connected to VCC. This prevents undefined behavior of the IC due to floating inputs.
  3. Output and Additional Control Lines:
    • Depending on your specific application, the outputs (A0-A2) from both U1 and U2 can be connected to subsequent parts of your circuit that require binary-encoded input. U1:9 (A0), U1:7 (A1), U1:6 (A2) and similarly for U2.
    • The Group Select (GS) outputs, U1:14 and U2:14, can be utilized to indicate when any input is active.
Note that the EO (Enable Output) of the last encoder in the cascade (U2 in this case, if not extending further) can be left unconnected if not used for further cascading or monitoring.
Please adjust the above connections based on your specific application needs, such as if you plan to use all input pins or have specific logic levels to maintain. Ensure all unused inputs are correctly terminated (usually tied to VCC or GND as per the logic level needed to deactivate them) to prevent unexpected behavior.
1y
danniell

danniell

@copilot necesito conectar u1 y u2 en cascada de tal manera para tener 16 entradas y 4 salidas
1y

copilot

Para conectar U1 y U2 en cascada con el objetivo de tener 16 entradas y 4 salidas, suponiendo que U1 y U2 son codificadores de prioridad 8-a-3, puedes seguir una configuración que permita concatenar las entradas y las salidas para manejar 16 entradas y generar 4 salidas codificadas. Aquí te proporciono una guía general sobre cómo hacerlo:
  1. Conexiones de Alimentación:
    • Conecta U1:VCC y U2:VCC al voltaje positivo de alimentación.
    • Conecta U1:GND y U2:GND al voltaje de tierra (GND).
  2. Conexiones para Cascada:
    • Para expandir las entradas de 8 a 16, debemos conectar el Enable Output (EO) de U1 al Enable Input (EI) de U2. Esto permite que U2 se active solo cuando U1 no está satisfaciendo ninguna condición de entrada.
    • Asegúrate de que todas las entradas no utilizadas en ambos U1 y U2 estén conectadas a un estado lógico alto (VCC) para evitar entradas flotantes.
  3. Control de Las Salidas:
    • Los outputs de U1 y U2 (A0, A1, y A2 de cada uno) se conectarán a las entradas de un tercer componente que combine las salidas 3-a-3 de cada U1 y U2 a una salida final de 4 bits. Este componente puede ser un codificador adicional o una lógica personalizada.
    • La salida de U1 se utilizará para indicar las 8 entradas inferiores, y la salida de U2 para las 8 entradas superiores. La lógica de combinación necesitará manejar estos rangos para producir una salida de 4 bits adecuada.
  4. Combinación de Salidas:
    • Para combinar las salidas de U1 y U2 en una sola salida de 4 bits, es posible emplear un microcontrolador, una serie de puertas lógicas adicionales, o incluso otro codificador, dependiendo de tus requisitos específicos.
    • Una opción es usar las salidas GS (Group Select) de U1 y U2 para determinar cuál de los codificadores está activo y, con base en esa información, ajustar la salida de 4 bits correspondiente.
Sin tener los detalles específicos de cada U1 y U2 (por ejemplo, si son chips específicos con capacidades de cascada integradas), esta es una guía general. Dependiendo del chip específico, es posible que haya formas más eficientes o características integradas que simplifiquen la conexión.
Es importante revisar las hojas de datos de los componentes específicos que estás utilizando para asegurarte de que las conexiones sean compatibles con sus requisitos eléctricos y lógicos. Además, considera la posibilidad de utilizar resistencias pull-up o pull-down para las entradas no utilizadas, según lo que recomiende la hoja de datos.
1y
1
U1 VCC - U2 VCC
U1 A2 - U2 A2
U1 A2 - U2 A2
U1 E0 - U2 EI
U1 VCC - U2 VCC
U1 E0 - U2 EI
U2
End of Life
U1 GND - U2 GND
U1 A0 - U2 A0
U1 A1 - U2 A1
U1 (7) - U2 (4)
U1 A1 - U2 A1
U1 GND - U2 GND
U1 A0 - U2 A0
U1 GS - U2 GS
U1
End of Life
U1 GS - U2 GS
U1 (7) - U2 (4)
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