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3221 RS-232 driver/receiver auto-powerdown mode
In the SN65C3221/SN75C3221 datasheet, the "auto-powerdown" (low power/sleep) mode is described like this:
"During this mode of operation, if the devices do not sense a valid RS-232 signal on the receiver input, the driver output is disabled."
Does this mean that a signal on the RX line is the ONLY way auto-powerdown mode can be exited? In other words, if the chip enters auto-powerdown mode and disables the driver output, does not receive any signal on the receiver, but then a signal is supplied to the TX line, will it power up the driver and send out the message?
Thank you for your help -
Hello Meredith,The second way to exit "auto-power down" is to apply a logic high to the "FORCEON" input. It will take about 30uS (Data sheet typical say 100uS) between exiting "auto-power down" before the driver will be ready to send.The charge pump is refilling during this time.
Regards,Ronald MichallickLinear Applications
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I just noticed that the typical spec is supply enable time is 100uS on page 6 of the data sheet.
Ron, thanks for your responses. So simply applying a signal to the TX line is not sufficient to exit powerdown mode; I must assert FORCEON. Correct?
Thanks for your help!
Your understanding is correct.
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