DP83905AVQB National Semiconductor, DP83905AVQB Datasheet - Page 44

• Manufacturer Part Number: DP83905AVQB
• Description: IC CONTROLR AT/LAN TP IN 160PQFP
• Manufacturer: National Semiconductor
• Series: AT/LANTIC™r

Specifications of DP83905AVQB

• Controller Type: AT, LAN Twisted-Pair Interface Controller
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 100mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 160-BFQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Interface: -
• Other names: *DP83905AVQB

6 0 Operation of AT LANTIC Controller
the CRC generator Packets with improper CRC will be re-
jected The AUTODlN II (X
X
polynomial is used for the CRC calculations
6 2 BUFFER MEMORY ACCESS CONTROL (DMA)
The buffer memory control capabilities of the AT LANTIC
Controller greatly simplify the use of the AT LANTIC Con-
troller in typical configurations The local DMA channel
transfers data between the FIFO and memory On transmis-
sion the packet is DMA’d from memory to the FIFO in
bursts Should a collision occur (up to 15 times) the packet
is re-transmitted with no processor intervention On recep-
tion packets are moved via DMA from the FIFO to the re-
ceive buffer ring (as explained below)
12
a
X
11
a
X
10
a
X
8
a
32
X
a
7
a
X
26
X
5
FIGURE 27 AT LANTIC Controller Bus Architecture
a
a
X
X
23
4
a
a
X
X
22
2
a
a
X
1
X
16
a
a
1)
44
(Continued)
A Remote DMA channel is also provided on the AT LANTIC
Controller to accomplish transfers between a buffer memory
and an internal Data Port when using the AT LANTIC Con-
troller in I O Mode This Remote DMA channel is not used
when the AT LANTIC Controller is used in a shared Memo-
ry mode In this second mode the buffer memory is dual
ported and directly mapped into the system memory In this
mode the system CPU directly accesses the RAM under
software control to transfer packet data
The following sections describe the operation of the Local
DMA channel for packet reception which is used in both
modes For Shared Memory mode the description of the
Remote DMA does not apply
For reference an example configuration using the AT LAN-
TIC Controller is shown in Figure 27
TL F 11498 – 24