CS8920A View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
'CS8920A' PDF : 144 Pages View PDF
CS8920A
Receive and Transmit Frame Locations
The Receive and Transmit Frame PacketPage lo-
cations are used to transfer Ethernet frames to
and from the host. The host simply writes to and
reads from these locations, and internal buffer
memory is dynamically allocated between trans-
mit and receive as needed. This provides more
efficient use of buffer memory and better overall
network performance. As a result of this dynamic
allocation, only one receive frame (starting at
PacketPage base + 0400h) and one transmit
frame (starting at PacketPage base + 0A00h) are
directly accessible. See Section 4.9.
4.2 PacketPage Memory Map
Table 4.1 shows the CS8920A PacketPage mem-
ory address map:
Table 4.1 is continued on the next page.
Base
+
0000h
0004h
0026h
0028h
002Ah
002Ch
0040h
0042h
0044h
0048h
004Ah
0050h
0052h
0100h
0120h
0140h
0142h
# of
Bytes
4
34
2
2
2
20
2
2
4
2
6
2
174
32
32
2
2
Type
Read-only
Read-only
Read-only
Read-only
Read/Write
Read/Write
Read
Read/Write
Read-only
Read-only
Description
Cross
Reference
Bus Interface Registers
32-bit Product Identification Code
Section 4.3
Reserved
Note 2
ISA RxDMA Start of Frame 16-bit Offset to Status
Sections 4.3, 4.12
ISA RxDMA 12-bit Frame Count
Sections 4.3
ISA RxDMA Byte Count 16 bit
Sections 4.3
Reserved. Do Not Write to This Space.
Note 2
EEPROM Command Register
Sections 3.6, 4.3
EEPROM Data Word
Sections 3.6, 4.3
Reserved. Do Not Write to This Space.
Note 2
Link Partner Ability in Auto Negotiation
Note 2
Reserved. Do Not Write to This Space.
Sections 3.6, 4.3
Receive Frame byte counter
Sections 4.3, 5.2.9
Reserved
Note 2
Status and Control Registers
CS8920A Config/Control Registers (two bytes per coded Section 4.4, 4.5
value)
CS8920A Status/Event Registers, ISQ is 0120h
Section 4.4, 4.5
Reserved. Do Not Use.
Note 2
Reserved. Do Not Write to This Space.
Note 2
NOTES: 1) All registers are accessed as words only.
2) Read operation from the reserved location provides undefined data. Writing to a reserved location or
undefined bits may result in unpredictable operation of the CS8920A.
Table 4.1. PacketPage Memory Address Map
40
DS238PP2
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