Cs8900a – Cirrus Logic CS8900A User Manual

Page 54

DS271F5

CS8900A

Crystal LAN™ Ethernet Controller

CIRRUS LOGIC PRODUCT DATASHEET

RegNum

The lower six bits describe which register (4, 8, C, 10 or 12) is contained in the ISQ.

RegContent

The upper ten bits contain the register data contents.

Reset value is: 0000 0000 0000 0000

4.4.6 Register 3: Receiver Configuration

(RxCFG, Read/Write, Address: PacketPage base + 0102h)

RxCFG determines how frames will be transferred to the host and what frame types will cause interrupts.

000011

These bits provide an internal address used by the CS8900A to identify this as the Receiver

Configuration Register.

Skip_1

When set, this bit causes the last committed received frame to be deleted from the receive buf-

fer. To skip another frame, the host must rewrite a “1” to this bit. This bit is not to be used if
RxDMAonly (Bit 9) is set. Skip_1 is an Act-Once bit. See Section 5.2.5 on page 85.

StreamE

When set, StreamTransfer mode is used to transfer receive frames that are back-to-back and

that pass the Destination Address filter (see Section 5.2.10 on page 87). When StreamE is
clear, StreamTransfer mode is not used. This bit must not be set unless either bit AutoRxDMA
or bit RXDMAonly is set.

RxOKiE

When set, there is an RxOK Interrupt if a frame is received without errors. RxOK interrupt is

not generated when DMA mode is used for frame reception.

RxDMAonly

The Receive-DMA mode is used for all receive frames when this bit is set.

AutoRxDMAE

When set, the CS8900A will automatically switch to Receive-DMA mode if the conditions spec-

ified in Section 5.4 on page 94 are met. RxDMAonly (Bit 9) has precedence over AutoRxD-
MAE.

BufferCRC

When set, the received CRC is included with the data stored in the receive-frame buffer, and

the four CRC bytes are included in the receive-frame length (PacketPage base + 0402h). When
clear, neither the receive buffer nor the receive length include the CRC.

CRCerroriE

When set, there is a CRCerror Interrupt if a frame is received with a bad CRC.

RuntiE

When set, there is a Runt Interrupt if a frame is received that is shorter than 64 bytes. The

CS8900A always discards any frame that is shorter than 8 bytes.

ExtradataiE

When set, there is an Extradata Interrupt if a frame is received that is longer than 1518 bytes.

The operation of this bit is independent of the received packet integrity (good or bad CRC).

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 3.3 on page 19.

Reset value is: 0000 0000 0000 0011