MOTOROLA
Chapter 28. SCC Ethernet Mode
28-11
Part V. The Communications Processor Module
Figure 28-5. MPC860 Ethernet Parallel CAM Interface
The SDACK1 and SDACK2 signals are asserted during all bus cycle writes of the frame
data. One SDACK1/SDACK2 combination identiÞes the Þrst 32 bits of the frame, another
identiÞes all mid-frame data, and a third identiÞes the last 32-bit bus write of the frame only
if the tag byte is appended. The tag byte is appended from the sample of PB(16Ð23) if
NOTE
:
The receive data is sent to the CAM as it is written to system memory. The SDACK1/SDACK2 signals are used to
identify the destination address and any other preferred frame bytes. The RSTRT signal is not required in this
conÞguration, although it is still available.
EEST
MC68160
TXD
TENA (RTS)
TCLK (CLKx)
RXD
RENA (CD)
RCLK (CLKx)
CLSN (CTS)
REJECT
Tx
TENA
TCLK
Rx
RENA
RCLK
CLSN
Loop
Passive
To Media
Tag
Destination
Data
Address
Destination
Address
Type/
Length
Source
Address
Frame Check
Sequence
1 Byte (Optional)
4 Byte
2 Bytes
6 Bytes
2 Bytes
46Ð1500 Bytes
4 Bytes
Parallel I/O
PB[16:23]
SDACK1/SDACK2
CAM Control
Optional Frame
Tag Byte
CAM
System
Bus
SDMA
SDACK2
SCC
Bus
Writes
Asserted for One
Cycle or Two 16-Bit
Write Cycles, etc.
Asserted on Each Write
Cycle to Memory up to
and Including the Last
System Bus Write
of the Frame
Frame can be Rejected if Asserted During
Frame Reception. Further Transmissions
on System Bus Cease and Buffer
Descriptors are Reused. SDACK1 Asserted
when New Frame Arrives
SigniÞes Last 32-Bit Bus
Write to Memory Only if
Tag Byte is Appended. Tag
Byte Could be Byte 0, 1, 2,
or 3 of the 32-Bit Write
SDACK1
REJECT
NOTE: The diagram shows SDMA system bus writes, not data on the RXD pin. Other bus activity can occur between
successive 32-bit writes. In such a case, SDACK1/SDACK2 would not be asserted for other bus activity.
MPC860
Содержание MPC860 PowerQUICC
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Страница 325: ...MOTOROLA Part IV Hardware Interface IV v Part IV Hardware Interface ...
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