SCC Ethernet Mode
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
27-15
27.17 Ethernet Mode Register (PSMR)
In ethernet mode, the protocol-specific mode register (PSMR), shown in
Figure 27-5
, is used as the
ethernet mode register.
Table 27-7
describes PSMR fields.
Non-Octet Error
(Dribbling Bits)
The ethernet controller handles up to seven dribbling bits when the receive frame terminates
nonoctet aligned. It checks the CRC of the frame on the last octet boundary. If there is a CRC error,
a frame nonoctet aligned error is reported, SCCE[RXF] is set, and the alignment error counter is
incremented. If there is no CRC error, no error is reported. The receiver then enters hunt mode.
CRC
When a CRC error occurs, the channel closes the buffer, sets SCCE[RXF] and CR in the RxBD, and
increments the CRC error counter (CRCEC). After receiving a frame with a CRC error, the receiver
enters hunt mode. CRC checking cannot be disabled, but CRC errors can be ignored if checking is
not required.
0
1
2
3
4
5
6
7
8
9
10
11
12
14
15
Field HBC
FC
RSH
IAM
CRC
PRO BRO
SBT
LPB
SIP
LCW
NIB
FDE
Reset
0000_0000_0000_0000
R/W
R/W
Addr
0xA28 (PSMR2), 0xA48 (PSMR3), 0xA68 (PSMR4)
Figure 27-5. Ethernet Mode Register (PSMR)
Table 27-7. PSMR Field Descriptions
Bits
Name
Description
0
HBC
Heartbeat checking
0 No heartbeat checking is performed. Do not wait for a collision after transmission.
1 Wait 20 transmit clocks or 2 µs for a collision asserted by the transceiver after transmission. The
HB bit in the TxBD is set if the heartbeat is not heard within 20 transmit clocks.
1
FC
Force collision
0 Normal operation
1 The channel forces a collision when each frame is sent. To test collision logic configure the
MPC885 in loopback operation. In the end, the retry limit for each transmit frame is exceeded.
2
RSH
Receive short frames
0 Discard short frames that are not as long as MINFLR.
1 Receive short frames.
3
IAM
Individual address mode
0 Normal operation. A single 48-bit physical address in PADDR1 is checked when it is received.
1 The individual hash table is used to check all individual addresses that are received.
4–5
CRC
CRC selection. Only CRC = 10 is valid. Complies with ethernet specifications. 32-bit CCITT-CRC.
X32 + X26 + X23 + X22 + X16 + X12 + X11 + X10 + X8 + X7 + X5 + X4 + X2 + X1 +1.
Table 27-6. Reception Errors (continued)
Error
Description
Summary of Contents for PowerQUICC MPC870
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