Thanks, David.
I have some questions concerning RXFIFO overflow. In CC2420ReceiveP.nc,
RXFIFO is flushed only when the length byte is invalid. So where is RXFIFO
overflow taken care of? Can reading bytes from RXFIFO automatically clear
the overflow status?
Also, in CC2420TransmitP, RXFIFO overflow status is not checked before
issuing the STXONCCA or STXON strobe. So if RXFIFO has already overflowed,
there will be no more space for ack frame. TinyOS 1.1.15 does do this check
before sending and flush RXFIFO accordingly even though I'm not sure if it
is for this purpose.
Thanks,
-Sha
--------------------------------------------------
From: "David Moss" <[EMAIL PROTECTED]>
Sent: Friday, March 14, 2008 5:26 PM
To: "'Liusand'" <[EMAIL PROTECTED]>; <[email protected]>
Subject: RE: [Tinyos-help] TXFIFO underflow not taken care of in TinyOS
2.0.2?
The TX FIFO is preloaded with data. The data is not being transmitted to
the CC2420 as the transmission is taking place, unlike other chips.
Because
of the preload, it is impossible for the CC2420 to produce a TXFIFO
UNDERFLOW. All the data to send is available on the chip when transmit
occurs.
Due to the rules of the CSMA and Transmit modules, a new packet cannot be
uploaded to the TX FIFO until the previous packet in the TX FIFO was
transmitted. This should guarantee that the TX FIFO be empty when the
next
transmit occurs. If a cancel occurs, a quick SFLUSHTX empties the
contents
of the TX FIFO.
-David
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Liusand
Sent: Friday, March 14, 2008 12:45 PM
To: [email protected]
Subject: [Tinyos-help] TXFIFO underflow not taken care of in TinyOS 2.0.2?
Hi,
When I was studying CC2420TransmitP.nc, I noticed that TXFIFO is never
flushed and underflow status is never checked. In CC2420RadioM.nc from
TinyOS 1.1.15, TXFIFO is flushed in startSend() every time before it is
written data to.
It might be too conservative in TinyOS 1.1.15, but why overflow is never
taken care of in TinyOS 2.0.2?
Another related question is, in which situations TXFIFO underflow may
happen?
Thanks,
Sha
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