MPC8536E-ANDROID Freescale Semiconductor, MPC8536E-ANDROID Datasheet - Page 912

• Manufacturer Part Number: MPC8536E-ANDROID
• Description: HARDWARE/SOFTWARE ANDROID OS
• Manufacturer: Freescale Semiconductor
• Series: PowerQUICC ™r
• Type: MPUr

Specifications of MPC8536E-ANDROID

• Contents: Board
• For Use With/related Products: MPC8536
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Enhanced Three-Speed Ethernet Controllers
After the buffer is filled, the eTSEC clears RxBD[E] and, if RxBD[I] is set, generates an interrupt. If the
incoming frame is larger than the buffer, the Ethernet controller fetches the next RxBD in the table. If it is
empty, the controller continues receiving the rest of the frame. In half-duplex mode, if a collision is
detected during the frame, no RxBDs are used; thus, no collision frames are presented to the user except
late collisions, which indicate LAN problems.
The RxBD length is determined by the MRBL field in the maximum receive buffer length register
(MRBLR). The smallest valid value is 64 bytes, with larger values being be some integral multiple of 64
bytes. During reception, the Ethernet controller checks for frames that are too short or too long. After the
frame ends (CRS is negated), the receive CRC field is checked and written to the data buffer. The data
length written to the last RxBD in the Ethernet frame is the length of the entire frame, which enables the
software to recognize an oversized frame condition.
Receive frames are not truncated when they exceed maximum frame bytes in the MAC’s maximum frame
register if MACCFG2[Huge Frame] is set, yet the babbling receiver error interrupt occurs
(IEVENT[BABR] is set) and RxBD[LG] is set.
After the receive frame is complete, the Ethernet controller sets RxBD[L], updates the frame status bits in
the RxBD, and clears RxBD[E]. If RxBD[I] is set, the Ethernet controller next generates an interrupt (that
can be masked) indicating that a frame was received and is in memory. The Ethernet controller then waits
for a new frame.
To interrupt reception or rearrange the receive queue, DMACTRL[GRS] must be set. If this bit is set, the
eTSEC receiver performs a graceful receive stop. The Ethernet controller stops immediately if no frames
are being received or continues receiving until the current frame either finishes or an error condition
occurs. The IEVENT[GRSC] interrupt event is signaled after the graceful receive stop operation is
completed. While in this mode the user can write to registers that are accessible to both the user and the
eTSEC hardware without fear of conflict, and finally clear IEVENT[GRSC]. After DMACTRL[GRS] is
cleared, the eTSEC scans the input data stream for the start of a new frame (preamble sequence and start
of frame delimiter), it resumes receiving, and the first valid frame received is placed in the next available
RxBD.
14.6.3.5
Ethernet Preamble Customization
By default eTSEC generates a standard Ethernet preamble sequence prior to transmitting frames.
However, the user can substitute a custom preamble sequence for the purpose of controlling switching
equipment at the receiver, particularly at 100/1000Mbps speeds. In FIFO mode preamble customization is
ignored; in any RMII mode only the standard preamble can be transmitted.
eTSEC normally searches for and discards the standard Ethernet preamble sequence upon receiving
frames. Part of the received preamble sequence can be optionally recovered and returned as part of the
frame data, making it visible to user software. Note however, that no preamble is received in FIFO mode,
and preamble cannot be recovered in any RMII mode. Note that it is also possible for the first two bytes
of custom preamble (PreOct0 and PreOct1) to be lost in during conversion to ten-bit code groups in the
PCS sub-layer. Thus is it recommended that any custom preamble start at PreOct2.
MPC8536E PowerQUICC III Integrated Processor Reference Manual, Rev. 1
14-164
Freescale Semiconductor