Can I say that in UART shift registers -

  1. UART Tx uses Parallel in Serial Out Shift registers - My reasoning is that we are writing complete byte but it will transmit bit by bit. True or False?

  2. UART Rx uses Serial in Parallel out shift registers - My reasoning is that we are receiving data in Serial but we will read data in parallel i.e. after 1 byte. True or False?

  • \$\begingroup\$ 1. and 2. depends on the UART \$\endgroup\$
    – jsotola
    Oct 7 '20 at 6:18
  • 1
    \$\begingroup\$ I can't say it's 100% true, but it's a natural thought to use the technique you mentioned, and it's easy to implement. \$\endgroup\$
    – Light
    Oct 7 '20 at 6:31
  • \$\begingroup\$ Yes it's true. It's not exactly correct, you should check the dataset to see the diagrams and circuits or just type in google UART block diagram, functional diagram. Otherwise you are correct, we just push out or push in a whole byte from a register. \$\endgroup\$ Oct 7 '20 at 7:41
  • \$\begingroup\$ There are a very few UARTs with SPI interfaces; these are serial-in serial-out but the vast majority are parallel on the ‘local’ side \$\endgroup\$
    – Frog
    Nov 3 '21 at 20:17

Welcome Tannoy,

If you take the example of a microcontroller, Yes it happens what you told in point 1 & point 2. But along with data bits, there are some control bits also get transmitted and received.

Below is a block diagram of STM8 microcontroller UART unit.

enter image description here

STM8S reference manual (RM0016)

  • 2
    \$\begingroup\$ Could you edit this to add text explanations for the OP? At present, it shows the diagram and RM0016 but explains little. \$\endgroup\$
    – TonyM
    Oct 7 '20 at 10:17

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