topic Re: SCI sending problem - MC9S12XS128 in S12 / MagniV Microcontrollers

SCI sending problem - MC9S12XS128

956326010 — Sat, 25 Feb 2017 03:12:02 GMT

Hello:

I have some problems with my freescale controller.

When I debug the SCI program, the value of the SCI1DRL register is always 0；for example，after runing "SCI1DRL = 0x55;" the value of SCI1DRL is 0x00,and the value of SCI1SR1_TDRE is always 1，using the serial port debugging assistant, the value of I get is 0x85.

When I run "SCI1DRL = 0xaa;/*SCI1DRL = other data;*/" ,the value of I get is wrong.

I want to know how to solve the problem.

Original Attachment has been moved to: main.c.zip

Re: SCI sending problem - MC9S12XS128

lama — Tue, 28 Feb 2017 10:41:52 GMT

Hi,

Each SCI has 2 Rx and 2 Tx registers.

Two Rx registers means SCIDR and its shift register.

Two Tx registers means SCIDR and its shift register.

The observer is able to see only 1 Rx and 1 Tx register even they have the same name SCIDR. The MCU recognizes access to these registers on the basis whether register is being read or written.

Remaining Rx and Tx registers are shift registers and they are not visible to user. So if you write to SCIDR and Rx shift register is empty then data are immediately shifted to this register and transmitting starts.

When data is receiving they are stored inside receive buffer and when the byte is completed it is shifted to Rx register SCIDR.

When we want to TX data then we write it into SCIDR register and it is consequently moved to a shift register. The user is not able to read these transmit registers..

I suggest you to test the SCI in loopback mode to be able to see in the Rx what you are sending in the Tx.

Best regards,

Ladislav

Re: SCI sending problem - MC9S12XS128

danielmartynek — Tue, 28 Feb 2017 11:58:40 GMT

You can look at the attached example.

Although it is written for S12XEP100, the SCI module is the same.

Regards

Daniel

Re: SCI sending problem - MC9S12XS128

956326010 — Wed, 01 Mar 2017 03:22:20 GMT

Thanks,I will go back to try again and feedback the result

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主题:Re: - Re: SCI sending problem - MC9S12XS128

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Re: SCI sending problem - MC9S12XS128

reply from Daniel Martynek in S12 / MagniV Microcontrollers - View the full discussion

�

You can look at the attached example.

Although it is written for S12XEP100, the SCI module is the same.

�

Regards

Daniel

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Re: SCI sending problem - MC9S12XS128

956326010 — Wed, 01 Mar 2017 03:29:25 GMT

Thanks!