Motorola MPC860 PowerQUICC User Manual page 774

Part V. The Communications Processor Module
Table 28-9. SCCE/SCCM Field Descriptions (Continued)
Bits Name
13 BSY Busy condition. Set when a frame is received and discarded due to a lack of buffers.
14 TXB Tx buffer. Set when a buffer has been sent on the Ethernet channel.
15 RXB Rx buffer. Set when a buffer that was not a complete frame was received on the Ethernet channel.
Figure 28-12 shows an example of interrupts that can be generated in Ethernet protocol.
Frame
Received in Ethernet
Time
RXD Line Idle
RENA
Ethernet SCCE
Events
NOTES
:
1. RXB event assumes receive buffers are 64 bytes each.
2. The RENA events, if required, must be programmed in the port C parallel I/O, not in the SCC itself.
3. The RxF interrupt may occur later than RENA due to receive FIFO latency.
Frame
Transmitted by Ethernet
TXD Line Idle
TENA
CLSN
Ethernet SCCE
Events
NOTES:
1. TXB events assume the frame required two transmit buffers.
2. The GRA event assumes a
3. The TENA or CLSN events, if required, must be programmed in the port C parallel I/O, not in the SCC itself.
LEGEND:
P = Preamble, SFD = Start frame delimiter, DA and SA = Source/Destination address,
T/L = Type/Length, D = Data, CR = CRC bytes
Figure 28-12. Ethernet Interrupt Events Example
Note that the SCC status register (SCCS) cannot be used with the Ethernet protocol. The
current state of the RENA and CLSN signals can be found in port C.
28-26
Stored in Rx Buffer
P SFD DA SA T/L
Stored in Tx Buffer
P SFD DA SA T/L
TXB
command was issued during frame transmission.
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MPC860 PowerQUICC UserÕs Manual
Description
D CR
RXB RXF
D CR
TXB, GRA
Line Idle
Line Idle
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