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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 BIT NAME BIT DESCRIPTION
1..0 IFSSelect 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.
4..2 Reserved Reserved for future use. Should be set to 0.
5 FullDuplexEnable 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.
6 RcvLargeFrames 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.
7 Reserved Reserved for future use. Should be set to 0.
8 FlowControlEnable 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.