Cs8900a – Cirrus Logic CS8900A User Manual

Page 56

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CS8900A

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4.4.8 Register 5: Receiver Control

(RxCTL, Read/Write, Address: PacketPage base +0104h)

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 5.2.10 on page 87.

000101

These bits provide an internal address used by the CS8900A 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 5.2.10 on page 87).

IAHashA

When set, receive frames are accepted when the Destination Address is an Individual Address

that passes the hash filter.

PromiscuousA

Frames with any address are accepted when this bit is set.

RxOKA

When set, the CS8900A accepts frames with correct CRC and valid length (valid length is: 64

bytes <= length <= 1518 bytes).

MulticastA

When set, receive frames are accepted if the Destination Address is an Multicast Address that

passes the hash filter.

IndividualA

When set, receive frames are accepted if the Destination Address matches the Individual Ad-

dress found at PacketPage base + 0158h to PacketPage base + 015Dh.

BroadcastA

When set, receive frames are accepted if the Destination Address is FFFF FFFF FFFFh.

CRCerrorA

When set, receive frames that pass the Destination Address filter, but have a bad CRC, are ac-

cepted. When clear, frames with bad CRC are discarded. See Note 5.

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
CS8900A discards any frame that is less than 8 bytes. See Note 5.

ExtradataA

When set, receive frames longer than 1518 bytes and that pass the Destination Address filter

are accepted. The CS8900A accepts only the first 1518 bytes and ignores the rest. When clear,
frames longer than 1518 bytes are discarded. See Note 5.

After reset, if no EEPROM is found by the CS8900A, then the register has the following initial state. If an EEPROM
is found, then the register's initial value may be set by the EEPROM. See Section 5.2.10 on page 87.

Reset value is: 0000 0000 0000 0101

Notes: 5. Typically, when bits CRCerrorA, RuntA and ExtradataA are cleared (meaning bad frames are being

discarded), 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.