DP83907VF National Semiconductor, DP83907VF Datasheet - Page 51

• Manufacturer Part Number: DP83907VF
• Description: IC CONTROLLR AT/LANII TP 160PQFP
• Manufacturer: National Semiconductor

Specifications of DP83907VF

• Controller Type: Network Interface Controller (NIC)
• Interface: Twisted Pair
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 150mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 160-MQFP, 160-PQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *DP83907VF

6 0 Operation of DP83907
The idle state is exited and the DP83907 will drive the local
memory bus when a request from the FIFO in the DP8390
(NIC) core causes the memory bus interface logic to issue a
read or write operation such as when the DP83907 is trans-
mitting or receiving data
The NIC Core’s Remote DMA also requests access from
the memory bus When software programs an I O data
transfer between the CPU and the buffer RAM the Remote
DMA controls this request
All Local DMA transfers are burst transfers the DMA will
transfer an exact burst of bytes programmed in the Data
Configuration Register (DCR) then relinquish the memory
bus If there are remaining bytes in the FIFO the next burst
will not be initiated until the FIFO threshold is exceeded
I O Mode Operation
In I O mode the DP83907 transfers data to and from the
packet buffer RAM by utilizing the Remote DMA logic which
is programmed by the main system CPU to transfer data
through the DP83907’s internal data
INTERLEAVED LOCAL REMOTE OPERATION
When in I O mode the remote DMA is used to transfer data
to from the main system If a remote DMA transfer is initiat-
ed or in progress when a packet is being received or trans-
mitted the Remote DMA transfers will be interrupted for
higher priority Local DMA transfers When the Local DMA
transfer is completed the Remote DMA will rearbitrate for
the bus and continue its transfers
If the FIFO requires service while a remote DMA is in prog-
ress the Local DMA burst is appended to the Remote Trans-
fer When switching from a local transfer to a remote trans-
fer there is a break to allow the CPU to fairly contend for the
bus
REMOTE DMA BI-DIRECTIONAL PORT
The Remote DMA transfers data between the local buffer
memory and the internal bi-directional port (memory to I O
transfer)
This transfer is arbitrated on a transfer by transfer basis
versus the burst transfer mode used for Local DMA trans-
fers This bi-directional port is integrated onto the DP83907
and is read written by the host All transfers through this
port are asynchronous At any one time transfers are limited
to one direction either form the port to local buffer memory
(Remote Write) or form local buffer memory to the port (Re-
mote Read)
FIGURE 38 I O Operation All Data Transfers and
Arbitration is Controlled by the NIC Core
(Continued)
TL F 12082– 33
51
I O MODE REMOVING PACKETS FROM RING
Network activity is isolated on a local bus where the
DP83907’s local DMA channel performs burst transfers be-
tween the buffer memory and the DP83907’s FIFO The Re-
mote DMA transfers data between the buffer memory and
the host memory via the internal bi-directional I O port The
Remote DMA provides local addressing capability and is
used as a slave DMA by the host The host system reads
the I O port to transfer data between the system and I O
port The DP83907 allows Local and Remote DMA opera-
tions to be interIeaved
Packets are removed from the ring using the Remote DMA
When using the Remote DMA the Send Packet command
can be used This programs the Remote DMA to automati-
cally remove the received packet pointed to by the Bounda-
ry Pointer At the end of the transfer the DP83907 moves
the Boundary Pointer freeing additional buffers for recep-
tion The Boundary Pointer can also be moved manually by
programming the Boundary Register Care should be taken
to keep the Boundary Pointer at least one buffer behind the
Current Page Pointer
Data transfer by the Remote DMA to the integrated I O data
port is dependent on whether the DP83907 is set into 8 bit
mode or 16 bit mode In 8 bit mode all transfers are 8 bits (1
byte) wide When in 16 bit mode all transfers are 16 bits (1
word) wide The data width is selected by setting the WTS
bit in the data Configuration Register and setting the DWID
pin for the proper mode
The following is a suggested method for maintaining the
Receive Buffer Ring pointers
1 At initialization set up a software variable (next pkt) to
2 When initializing the DP83907 Controller set
3 After a packet is DMAed from the Receive Buffer Ring
indicate where the next packet will be read At the begin-
ning of each Remote Read DMA operation the value of
next pkt will be loaded into RSAR0 and RSAR1
BNDRY
CURR
next pkt
the Next Page Pointer (second byte in the DP83907 Con-
troller buffer header is used to update BNDRY and
next pkt
FIGURE 39 1st Received Packet Removed
e
e
PSTART
e
PSTART
PSTART
by Remote DMA
a
1
a
1
TL F 12082 – 34