am79c961 Advanced Micro Devices, am79c961 Datasheet - Page 50

• Manufacturer Part Number: am79c961
• Description: Pcnettm-isa Jumperless Single-chip Ethernet Controller For Isa
• Manufacturer: Advanced Micro Devices

Polling
When there is no channel activity and there is no pre- or
post-receive or transmit activity being performed by the
PCnet-ISA
will periodically poll the current receive and transmit de-
scriptor entries in order to ascertain their ownership. If
the DPOLL bit in CSR4 is set, then the transmit polling
function is disabled.
1-524
AMD
RES
RLEN RES
TLEN RES
+
controller then the PCnet-ISA
CSR2
IADR[23:16]
PADRF[47:32]
LADRF[15:0]
LADRF[31:16]
LADRF[47:32]
LADRF[63:48]
Initialization
PADR[31:16]
PADR[15:0]
24-Bit Base Address
RDRA[15:0]
TDRA[15:0]
Initialization Block
MODE
Block
Pointer to
RDRA[23:16]
TDRA[23:16]
IADR[15:0]
CSR1
Initialization Block and Descriptor Rings
+
controller
P R E L I M I N A R Y
Buffers
Buffers
RCV
XMT
Am79C961
1st desc.
start
RMD0
1st desc.
start
A typical polling operation consists of the following: The
PCnet-ISA
scriptor address stored internally to vector to the
appropriate Receive Descriptor Table Entry (RDTE). It
will then use the current transmit descriptor address
(stored internally) to vector to the appropriate Transmit
Descriptor Table Entry (TDTE). These accesses will be
made to RMD1 and RMD0 of the current RDTE and
TMD0
RX DESCRIPTOR RINGS
RX DESCRIPTOR RINGS
RX DESCRIPTOR RINGS
Buffer
Buffer
Data
Data
1
1
RMD1 RMD2 RMD3
N
TMD1 TMD2 TMD3
RCV Descriptor
M
XMT Descriptor
+
Ring
controller will use the current receive de-
Ring
Buffer
Buffer
N
Data
Data
2
2
M
N
M
2nd desc.
start
2nd desc.
start
RMD0
N
TMD0
M
•
Buffer
Buffer
Data
Data
•
•
N
M
•
•
•
18183B-14
16907B-7