JAJSC32E September 2012 – June 2019 DP83848-EP
PRODUCTION DATA.
This register configures the RMII Mode of operation. When RMII mode is disabled, the RMII functionality is bypassed.
BIT | BIT NAME | DEFAULT | DESCRIPTION |
---|---|---|---|
15:6 | RESERVED | 0, RO | Reserved: Writes ignored, Read as 0 |
5 | RMII_MODE | Strap, RW | Reduced MII Mode: |
0 = Standard MII Mode | |||
1 = Reduced MII Mode | |||
4 | RMII_REV1_0 | 0, RW | Reduce MII Revision 1.0: |
0 = (RMII revision 1.2) CRS_DV will toggle at the end of a packet to indicate deassertion of CRS. | |||
1 = (RMII revision 1.0) CRS_DV will remain asserted until final data is transferred. CRS_DV will not toggle at the end of a packet. | |||
3 | RX_OVF_STS | 0, RO | RX FIFO Over Flow Status: |
0 = Normal | |||
1 = Overflow detected | |||
2 | RX_UNF_STS | 0, RO | RX FIFO Under Flow Status: |
0 = Normal | |||
1 = Underflow detected | |||
1:0 | ELAST_BUF[1:0] | 01, RW | Receive Elasticity Buffer: |
This field controls the Receive Elasticity Buffer which allows for frequency variation tolerance between the 50MHz RMII clock and the recovered data. The following values indicate the tolerance in bits for a single packet. The minimum setting allows for standard Ethernet frame sizes at ±50ppm accuracy for both RMII and Receive clocks. For greater frequency tolerance the packet lengths may be scaled (i.e. for ±100ppm, the packet lengths need to be divided by 2). | |||
00 = 14 bit tolerance (up to 16800 byte packets) | |||
01 = 2 bit tolerance (up to 2400 byte packets) | |||
10 = 6 bit tolerance (up to 7200 byte packets) | |||
11 = 10 bit tolerance (up to 12000 byte packets) |