Motorola MC68838 User Manual page 69

Table 7-1. RCCTLx and RPATHx Relationship
RCCTL RPATH
43 210 7654 3210
x0 000 k000 0000
k =
00 101 dddd dddd
00 001 dddd dddd
x0 F11 crrr DDSS
F =
c =
rrr =
DD =
SS =
xx 100 xxxx xxxx
xT F10 nnns ssss
T=
nnn =
sssss =
xx 100 xxxx xxxx
7-4
<--------------bit number
FILLER. Only START_DATA or FRAME_STATUS can follow this.
0 Between Frames
1 Before FS
START_DATA. RPATH contains the frame's FC. Only DATA and END_DATA can follow this.
DATA RPATHx. Holds two data symbols. Only DATA and END_DATA can follow this.
END_DATA. RPATHx contains status information describing the frame and why it ended. F is
the flush/retain bit. Only FRAME_STATUS and FILLER can follow this.
0 System interface must keep this frame.
1 System interface should discard this frame if possible.
0 Good CRC: FCS field of frame is valid, regardless of the type of frame.
1 Bad CRC: FCS field of frame is invalid. C = 1 is possible for void or is reserved for
implementor frame types.
Note that the C-bit is only valid if the reason field bits 654 = 000, which means normal
reception completed. In any other case, the CRC indication has no meaning.
111 MAC_Reset: Results from FSM transition R(30a).
110 Format Error: Results from FSM transition R(31b) or R(30b).
101 Fragment: Results from transition FSM R(31a).
100 Invalid Length: Frame ended normally with a T but it is too short or contains an odd
number of symbols. The last odd data symbol is discarded.
011 FSI abort: Frame ended because the FSI or other external logic asserted RABORT
during the reception of a frame.
010 DA Not Matched: MAC believes this frame is not addressed to it. DD = 00
(see below).
001 SA Matched: Frame ended because MAC believes that it sent this frame. Hence,
SS is not zero (see below).
000 Normal: Frame ended normally with a T. The frame could still have a CRC error.
11 Local match and DA <> 0: DA = MLA or MSA or broadcast (if enabled).
10 CAM interface match: MATCH or TR_BR_FWD is asserted but no local match i.e., not
MLA, MSA or broadcast. For normal, nonextended mode IGNORE_SACAM is false.
01 Promiscuous (if enabled): No local match, received in promiscuous mode.
00 No match: DA is not recognized and frame is not to be received promiscuously,
F = 1 on END_DATA.
11 Local match: SA = MLA or MSA and is not zero. SA could also be matched by the
CAM logic or otherwise satisfy the bridge-stripping algorithm.
10 CAM match and IGNORE_SACAM = 0: CAM finds an SA match but no local match
Note that SA could be zero and also satisfy the bridge-stripping algorithm.
01 Bridge match: CAM does not recognize the SA and no local match, but MAC
determines via the bridge-stripping algorithm (if enabled) that it sent this frame.
00 No match: This station did not send this frame.
Reserved for future use. Must be treated as FILLER.
FRAME_STATUS. RPATHx contains information on the received frame status indicators. (F
is the flush/retain bit described above.) The only time that F here differs from the F-bit on the
preceding END_DATA is when this frame is a secondary NSA frame to be discarded (F = 0 on
END_DATA, F = 1 here).
1 Indicates that this FS can be associated with a previously transmitted frame.
Usually, but not always, F = 1 when T = 1.
FS count field: Number of valid FS indicators present in sssss field.
FS indicator field: This field is filled from bit 4 to bit 0 as FS symbols are received (i.e., bit 4
contains the value of the first FS symbol received). 1 = S-symbol, 0 = R-symbol.
Reserved for future use. Must be treated as FILLER.
MC68838 USER'S MANUAL
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