QB4 ESCI question?

[edrian]

Hello,
I am using QB8 in a project where i will only use RX pin of ESCI and i would need an extra IO pin, my question is

Is that possible to use TX pin while ESCI is anabled? disabling TE pin would work?

thanks in advance

[erooll]

Hello.

Unfortunately, when you enable ESCI module, this pins Tx and Rx can not be used like general IO pins, even if Rx and Tx are disabled. the next text was taked from datasheet.

13.7.1 ESCI Transmit Data (TxD)
The TxD pin is the serial data output from the ESCI transmitter. When the ESCI is enabled, the TxD pin
becomes an output.
13.7.2 ESCI Receive Data (RxD)
The RxD pin is the serial data input to the ESCI receiver. When the ESCI is enabled, the RxD pin becomes
an input.

The only way to do this, is disable ESCI module, and then you can control this pin.

Regards

[edrian]

Thank you for your prompt answer,
I have build a board and tried to disable Transmitter TE bit, but wasn't able to control de pin, even though TE is disabled, ESCI enable bit is set and my guess is the TX pin is still routed to the peripheral, so i think i have a pin that can't use.

I was very active on yahoo groups, but it seems no one get there anymore, now i have found this one and i will login more often.

Edriano.

[bigmac]

Hello Edriano,

The data sheet for the 9S08 SCI module is a little less ambiguous, and should support the TxD pin being available as GPIO.  Perhaps the 9S08QG8 would be a better match to your requirements than the HC908QB8.  Of course, this will limit the supply voltage to 3.3 volt, rather than 5 volt.

Another alternative, capable of 5 volt operation, might be the 9S08SG8 or the 9S08SH8.  The SG8 does not seem to have a DIP version.

Regards,

Mac

[bigmac]

Hello, and welcome to the forum.

Since separate control bits are provided for transmit and receive, your assumption would seem reasonable.  Within the data sheet, in the list of features for the ESCI, this is further supported by the item "Separately enabled transmitter and receiver".

Regards,

Mac