CDK8920A View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
'CDK8920A' PDF : 144 Pages View PDF
CS8920A
Register 5: Receiver Control (RxCTL, Read/Write)
Address: PacketPage base + 0104h
F
E
D
C
B
A
9
8
7
6
5-0
ExtradataA RuntA CRCerrorA Broad IndividualA MulticastA RxOKA
castA
Promis IAHashA 000101
cuousA
RxCTL has two functions: Bits 8, C, D, and E define what types of frames to accept; Bits 6, 7, 9, A, and B
configure the Destination Address filter. See Section 5.3.
BIT NAME
DESCRIPTION
5-0 000101
These bits provide an internal address used by the CS8920A to identify this as the
Receiver Control Register.
For a received frame to be accepted, the Destination Address of that frame must pass
the filter criteria found in Bits 6, 7, 9, A, and B (see Section 5.3).
6
IAHashA
When set, receive frames are accepted when the Destination Address is an Individual
Address that passes the hash filter.
7
PromiscuousA Frames with any address are accepted when this bit is set.
8
RxOKA
When set, the CS8920A accepts frames with correct CRC and valid length 64 bytes <=
length <= 1518 bytes).
9
MulticastA
When set, receive frames are accepted if the Destination Address is a Multicast
Address that passes the hash filter.
A
IndividualA
When set, receive frames are accepted if the Destination Address matches the
Individual Address found at PacketPage base + 0158h to PacketPage base + 015Dh.
B
BroadcastA When set, receive frames are accepted if the Destination Address is FFFF FFFF
FFFFh.
C CRCerrorA When set, receive frames that pass the Destination Address filter, but have a bad CRC,
are accepted. When clear, frames with bad CRC are discarded. See Note 1.
D RuntA
When set, receive frames that are smaller than 64 bytes, and that pass the Destination
Address filter are accepted. When clear, received frames less that 64 bytes in length
are discarded. The CS8920A discards any frame that is less than 8 bytes. See Note 1.
E
ExtradataA
When set, receive frames longer than 1518 bytes and that pass the Destination
Address filter are accepted. The CS8920A accepts only the first 1518 bytes and
ignores the rest. When clear, frames longer than 1518 bytes are discarded. See Note 1.
After reset, if no EEPROM is found by the CS8920A, the register has the following initial state. If an EEPROM is
found, the register’s initial value may be set by the EEPROM. See Section 3.3.
0000 0000 0000 0101
NOTE:
1. Typically, when bits CRCerrorA, RuntA, and ExtradataA are cleared (meaning bad frames are being dis-
carded), then the corresponding bits CRCerroriE, RuntiE, and ExtradataiE should be set in register 3 (Receiver
Configuration register) to allow the device driver to keep track of discarded frames.
DS238PP2
53
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