DP83907VF National Semiconductor, DP83907VF Datasheet - Page 52

• 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
next pkt
BNDRY
If BNDRY
Note the size of the Receive Buffer Ring is reduced by one
256-byte buffer this will not however impede the operation
of the DP83907 The advantage of this scheme is that it
easily differentiates between buffer full and buffer empty it
is full if BNDRY
If in I O mode send packet is used to empty the buffer ring
this scheme cannot be used BNDRY must be initialized
equal to CURR or the first executed send packet will not
return data from the received packet which will be written at
CURR The Overwrite Warning bit of the Interrupt Status
Register must be used in this mode to differentiate between
buffer full and buffer empty
I O REMOTE DMA COMMANDS
The Remote DMA channel is used in the I O Mode to both
assemble packets for transmission and to remove received
packets from the Receive Buffer Ring It may also be used
for moving blocks of data or commands between host mem-
ory and local buffer memory (In Shared Memory Mode the
Remote DMA should be disabled and not used Packet
transfer to from the system is accomplished by normal CPU
read write operations )
e
e
k
Next Page Pointer
Next Page Pointer
PSTART then BNDRY
e
CURR empty when BNDRY
b
FIGURE 40 Remote DMA Auto Initialization from Buffer Ring
1
e
PSTOP
(Continued)
b
e
CURR-1
1
52
There are three modes of Remote DMA operation Remote
Write Remote Read or Send Packet
Two register pairs are used to control the Remote DMA a
Remote Start Address (RSAR0 RSAR1) and a Remote
Byte Count (RBCRO RBCR1) register pair The Start Ad-
dress Register pair points to the beginning of the block to be
moved while the Byte Count Register pair is used to indicate
the number of bytes to be transferred Full handshake logic
is provided to move data between local buffer memory and
a bi-directional I O port
Remote Write A Remote Write transfer is used to move a
block of data from the host into local buffer memory The
Remote DMA will read data from the I O port and sequen-
tially write it to local buffer memory beginning at the Remote
Start Address The DMA Address will be incremented and
the Byte Counter will be decremented after each transfer
The DMA is terminated when the Remote Byte Count Regis-
ter reaches a count of zero
Remote Read A Remote Read transfer is used to move a
block of data from local buffer memory to the host The
Remote DMA will sequentially read data from the local buff-
er memory beginning at the Remote Start Address and
write data to the I O port
TL F 12082 – 35