Sundance Spas ST201 manual Macctrl, BIT BIT Name

Sundance Technology

ST201

PRELIMINARY draft 2

MACCTRL
Class	I/O Registers, Control and Status
Base Address	IoBaseAddress register value
Address Offset	0x50
Access Mode	Read/Write
Width	32 bits

This register provides for setting of MAC-specific parameters. It is cleared upon reset.

BIT

1..0

4..2

5

6

7

8

BIT NAME

IFSSelect

Reserved

FullDuplexEnable

RcvLargeFrames

Reserved

FlowControlEnable

BIT DESCRIPTION

This field is used to select the size of Inter-Frame Spacing (IFS). By programming a larger number of bit times for the IFS, the ST201 will become less “aggressive” on the network and may defer more than normal. The performance of the ST201 may decrease as the IFS value is increased from the standard value. This, however, will prevent the ST201 from “capturing”the network.

00:no IFS extension, IFS = 96 BT (802.3 standard value).

01:IFS extended by 32 BT, IFS = 128 BT.

10:IFS extended by 128 BT, IFS = 224 BT.

11:IFS extended by 448 BT, IFS = 544 BT.

Reserved for future use. Should be set to 0.

Setting this bit configures the ST201 to function in a full duplex man- ner. Specifically, it disables transmitter deference to receive traffic, allowing simultaneous receive and transmit traffic. It has the side-effect of disabling CarrierSenseErrors statistics collection, since full duplex operation requires carrier sense to be masked to the transmitter. TxRe- set and RxReset bits in AsicCtrl must be set after changing the value of this bit.

This bit determines the frame size at which the OversizedFrame error is generated for receive frames. When RcvLargeFrames is cleared, minimum OversizedFrame size is 1514 bytes. When RcvLargeFrames is set, minimum OversizedFrame size is 4491 bytes. (This value was the maximum FDDI frame size of 4500 bytes, subtracting bytes for fields that have no Ethernet equivalent.)

The frame size at which an OversizedFrame error will be flagged includes the destination and source addresses, the type/length field, and the FCS field.

Reserved for future use. Should be set to 0.

Flow control enable. When it is cleared (default), the ST201 treats all incoming frames as data frames. When it is set, Flow control is enabled and the ST201 will act upon incoming flow control PAUSE frame. Note that FlowControlEnable should not be set unless FullDu- plexEnable is also set.

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