Maxim Integrated DS33R11 - Manual (Page 178)

DS33R11 Ethernet Mapper with Integrated T1/E1/J1 Transceiver
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Register Name: SU.LPBK
Register Description: Ethernet Interface Loopback Control Register
Register Address: 14Fh
Bit
# 7 6 5 4 3 2 1 0
Name - - - - - - - QLP
Default 0 0 0 0 0 0 0 0
Bit 0: Queue Loopback Enable (QLP) If this bit is set to 1, data from the Ethernet Interface receive queue is
looped back to the transmit queue. Buffered data from the serial interface will remain until the loopback is removed.
Register Name:
SU.GCR
Register Description: Ethernet Interface General Control Register
Register Address: 150h
Bit
# 7 6 5 4 3 2 1 0
Name - - - - CRCS H10S ATFLOW JAME
Default 0 0 0 0 0 0 1 0
Bit 3: CRCS If this bit is zero (default), the received MAC or Ethernet Frame CRC is stripped before the data is
encapsulated and transmitted on the serial interface. Data received from the serial interface is decapsulated, a
CRC is recalculated and appended to the packet for transmission to the Ethernet interface. If this bit is set to 1, the
CRC is not stripped from received packets prior to encapsulation and transmission to the serial interface, and data
received from the serial interface is decapsulated directly. No CRC recalculation is performed on data received
from the serial interface. Note that the maximum packet size supported by the Ethernet interface is still 2016 (this
includes the 4 bytes of CRC).
Bit 2: H10S This bit controls the 10/100 selection for RMII and DCE Mode. When in RMII mode, setting this bit to
1 will cause the MAC will operate at 100 Mbps and setting this bit to zero will cause the MAC to operate at 10
Mbps. When in DCE mode, the bit function is inverted – setting this bit to 1 will cause the MAC to operate at 10
Mbps. In DTE and MII mode, the MAC determines the data rate from the incoming TX_CLK and RX_CLK.
Bit 1: Automatic Flow Control Enable (ATFLOW) If this bit is set to 1, automatic flow control is enabled based on
the connection receive queue size and high watermarks. Pause frames are sent automatically in full duplex mode.
The pause time must be programmed through
SU.MACFCR . The jam sequence will not be sent automatically in
half duplex mode unless the JAME bit is set. This bit is applicable only in software mode.
Bit 0: Jam Enable (JAME) If this bit is set to 1, a Jam sequence is sent for a duration of 4 bytes. This function is
only valid in half duplex mode, and will only function if Automatic Flow Control is disabled. Note that if the receive
queue size is less than receive high threshold, setting a JAME will JAM one received frame. If JAME is set and the
receiver queue size is higher than the high threshold, all received frames are jammed until the queue empties
below the threshold.
Note that SU.GCR is only valid in the software mode.