EUSART vs. MSSP

[HenrikOlsson]

I'd still like to know more about the differences between MSSP and EUSART though

EUSART = Enhanced Universal Asynchronous Receiver Transceiver
MSSP = Master Synchronous Serial Port

Asynchronous means there is no dedicated clock line/signal, while synchronous means there IS a clock line/signal. RS232 is an asynchronous communication standard while for example SPI and I2C are synchronous.

/Henrik.

[keithv]

EUSART = Enhanced Universal Asynchronous Receiver Transceiver
MSSP = Master Synchronous Serial Port

Asynchronous means there is no dedicated clock line/signal, while synchronous means there IS a clock line/signal. RS232 is an asynchronous communication standard while for example SPI and I2C are synchronous.

/Henrik.

Can you give me a practical example of where it would be beneficial to have a dedicated clock line and also to not have a dedicated clock line?

[mpgmike]

If you have 2 PIC processors clocked at the same Fosc talking to each other, Asynchronous saves the clock pin. However, if you are talking to a peripheral with no oscillator (internal or external), it needs a way to know when to look at the data pin (or port) to take a picture & extract the data. Here the clock pin is necessary. The clock pin also keeps timing issues clean when communicating between 2 devices that don't share the same Fosc. The faster the communication, the more critical timing becomes.

[tumbleweed]

Synchronous devices typically latch the data on the clock edges, while async devices usually sense a change in the data,
wait a bit, and then begin sampling the signal one or more times to determine the logic state.

If you have long lines with mismatched impedance where the signals ring a lot, or a lot of delay/skew between the signals
then you can get false or mis-timed clocks and the data is corrupted. Since sync depends on a clock edge it also tends to be more susceptible to noise.

The delay in an async scheme allows time for the signal to settle giving you a better chance of reading the data correctly.

[Charlie]

In practical terms, the device you want to talk to usually determines. If you are talking to a computer it will likely be RS-232 serial port you need the EUSART. If you are designing both ends, use whatever you like.

[keithv]

That helps a lot. Thanks guys!