Sundance Spas ST201 - Manual (Page 34)

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Sundance Technology ST201 PRELIMINARY draft 2
22..21 Reserved Reserved for future use. Should be set to 0.
23 DribbleBits Indicates that the frame had accompanying dribble bits. This bit is
informational only, and does not indicate a frame error.
24 RxDMAOverflow Indicates that the RFD had insufficient buffer space for the frame data
and there were still data left to be transferred by RxDMA when the
ST201 ran out of fragment space. The ST201 will transfer what it can
into the buffers provided, discard the remainder of the frame and set
this bit.
27..25 Reserved Reserved for future use. Should be set to 0.
28 ImpliedBufferEn-
able This bit enables a special RxDMA mode. Setting this bit instructs the
ST201 not to fetch any RxDMAFragAddr/RxDMAFragLen entries from
this RFD. Instead, the ST201 assumes there is one receive buffer of
length 1528 bytes, starting immediately after ReceiveFrameStatus at
(RFD address + 8).
The host system sets this bit when it prepares the RFD. The ST201
tests this bit before RxDMA a frame, at the same time it tests the RxD-
MAComplete bit. When the ST201 updates ReceiveFrameStatus at the
end of the RxDMA operation (in order to set RxDMAComplete), the
value written to ImpliedBufferEnable is undefined. A driver cannot
assume a certain value is left in this bit after the RFD is used. There-
fore, the driver must write the desired value to this bit every time it
releases a RFD to the ST201. This mode of operation reduces the
number of information fetches by the ST201, and is intended for server
applications in which frames are received into a ring of maximum frame
sized buffers.
31..29 Reserved Reserved for future use. Should be set to 0.
BIT BIT NAME BIT DESCRIPTION