DP83901AV National Semiconductor, DP83901AV Datasheet - Page 12

• Manufacturer Part Number: DP83901AV
• Description: IC CONTROLLR SER NETWK IN 68PLCC
• Manufacturer: National Semiconductor

Specifications of DP83901AV

• Controller Type: Serial Network Interface Controller
• Interface: Serial
• Voltage - Supply: 5V
• Current - Supply: 110mA
• Mounting Type: Surface Mount
• Package / Case: 68-LCC (J-Lead)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Operating Temperature: -
• Other names: *DP83901AV

7 0 Packet Reception
LINKING RECEIVE BUFFER PAGES
If the length of the packet exhausts the first 256-byte buffer
the DMA performs a forward link to the next buffer to store
the remainder of the packet For a maximal length packet
the buffer logic will link six buffers to store the entire packet
Buffers cannot be skipped when linking a packet will always
be stored in contiguous buffers Before the next buffer can
be linked the Buffer Management Logic performs two com-
parisons The first comparison tests for equality between
the DMA address of the next buffer and the contents of the
Page Stop Register If the buffer address equals the Page
Stop Register the buffer management logic will restore the
DMA to the first buffer in the Receive Buffer Ring value
programmed in the Page Start Address Register The sec-
ond comparison tests for equality between the DMA ad-
1) Check for
2) Check for
e
e
to PSTOP
to Boundary
(Continued)
Linking Receive Buffer Pages
12
dress of the next buffer address and the contents of the
Boundary Pointer Register If the two values are equal the
reception is aborted The Boundary Pointer Register can be
used to protect against overwriting any area in the receive
buffer ring that has not yet been read When linking buffers
buffer management will never cross this pointer effectively
avoiding any overwrites If the buffer address does not
match either the Boundary Pointer or Page Stop Address
the link to the next buffer is performed
Linking Buffers
Before the DMA can enter the next contiguous 256-byte
buffer the address is checked for equality to PSTOP and to
the Boundary Pointer If neither are reached the DMA is
allowed to use the next buffer
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