Parity Modes

[Darrel Taylor]

Hi Sphere,

If I understand correctly, you want to change parity modes at Run-Time?

If so, then you are correct. Using either HSEROUT or SEROUT2 you can only change them at Compile-Time.

If you generate your own parity, and manipulate the registers manually, you can use the USART in 9-bit mode to get the 8E1 and 8O1, and turn off 9-bit mode for 8N1.

[Sphere]

Thanks for the reply, you where correct about changing parity modes at Run-Time? but still being relativity green around the ears regarding pbp how do I do this.

Thanks Sphere.

[Darrel Taylor]

Well, first let's look at how the parity works.

It's calulated by counting the number of 1's in the byte. For instance the letter "J" which is 01001010, 3 bits are a 1.

If using EVEN parity, the parity bit will be set to 0, since 3 is not an even number. ODD parity would be 1, if used.

For the letter "K" 01001011, 4 bits are a 1. So EVEN parity = 1, ODD = 0.

As for sending that via the USART ...
First, set up SPBRG, TXSTA and RCSTA like normal. (many other posts here show how to do that)

Set TXSTA.6 (TX9) to 1.   Selects 9-bit transmission
The parity bit goes in TXSTA.0 (TX9D)   9th bit of Transmit Data
Then put the byte to be sent in TXREG
and away she goes.

[Sphere]

Ill give it a go over the weekend.
Thanks again Sphere.