Questions of TL16C550D (Unexpected interrupts occure)

Sungyeol Park

Prodigy 100 points

Hello,

I used TL16C550DIZQS, BGA Package type for UART communication.

In ZQS package, It doesn't have /RI, /DCD, /DSR pin but sometimes it make interrupts from DSR, RI, DCD.

When Interrupts occure from DSR, RI, DCD, it doesn't work, so I disabled Modem status Interrupt, it works well.

Why interrups occure from inexistence pins?

Thanks.

over 7 years ago

0 Clemens Ladisch over 7 years ago

Guru 277170 points

The die is the same; these signals still exist inside the chip, they just aren't connected to any pin. It's exactly the same as if you were using a larger package and did not connect those pins.

0 Sungyeol Park over 7 years ago in reply to Clemens Ladisch

Prodigy 100 points

Thanks for reply.
But I can't understand, why interrups occured from 'NC' pins?
These interrups rarely happen, when repeating turn ON and OFF.

0 Clemens Ladisch over 7 years ago in reply to Sungyeol Park

Guru 277170 points

These pins are CMOS inputs, so they must not float. (See Implications of Slow or Floating CMOS Inputs (SCBA004).)

It appears that in the ZQS package, these pins do float, so they will increase power consumption, and might switch randomly. This would be a horrible bug.

0 Sungyeol Park over 7 years ago in reply to Clemens Ladisch

Prodigy 100 points

Thanks for Reply!

Interface

Interface forum

Questions of TL16C550D (Unexpected interrupts occure)