Re: What is Trigger Level in UART?

On Thu, 17 May 2007, google-rambo88 wrote:
Hi,
What is Trigger Level in UART?
I heard that We can commonly adjust it as 1, 4, 8 with setserial
command..

There are some buffers for receive / transmission in a UART. Say, in a plain 16550A, there are 16 bytes FIFO buffer for transmission, and another 16 bytes receive buffer.

One can program a UART to trigger an interrupt signal when a certain number of bytes are received (and occupied the receive buffer), or to trigger an interrupt when there are a few bytes free in the transmission buffer.

The design of the TX/RX buffers is to reduce no. of interrupt signals to the host system, so that, overhead of interrupt service routine can be reduced.

In some (more advanced) UART, there are larger RX/TX buffers, say 1kB x 2 on chip.

My 2 cents.

Stephen Wong @ Hong Kong

.

Relevant Pages

  • Re: What is Trigger Level in UART?
    ... plain 16550A, there are 16 bytes FIFO buffer for transmission, and another 16 bytes receive buffer. ... One can program a UART to trigger an interrupt signal when a certain number of bytes are received, or to trigger an interrupt when there are a few bytes free in the transmission buffer. ...
    (comp.os.linux.misc)
  • Re: [Ocfs2-devel] [PATCH 01/35] jbd2: Add buffer triggers
    ... This adds triggers to jbd2 buffer heads. ... an abort trigger will be ... used for non-buffer-related events like transaction completion. ... journal/transaction wide triggers should be implemented separately. ...
    (Linux-Kernel)
  • [PATCH 01/35] jbd2: Add buffer triggers
    ... This adds triggers to jbd2 buffer heads. ... an abort trigger will be ... used for non-buffer-related events like transaction completion. ... journal/transaction wide triggers should be implemented separately. ...
    (Linux-Kernel)
  • Re: Linux serial port dropping bytes
    ... UART is on a slow bus, you should be able to read out characters ... interrupt itself - context switches, cache misses, etc. That's ... why you use a UART with a buffer - it takes virtually the same ...
    (comp.arch.embedded)
  • Re: MFC Not Triggering OnReceive
    ... simple program that listens for a connection, ... program and i cannot get myonReceiveto trigger. ... when i send data to it the buffer receives the data but theonReceive ... the framework automatically calls the OnReceive function. ...
    (microsoft.public.vc.mfc)