MCIMX257CJM4 Freescale, MCIMX257CJM4 Datasheet - Page 89

• Manufacturer Part Number: MCIMX257CJM4
• Manufacturer: Freescale

Specifications of MCIMX257CJM4

• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

3.7.9.3
In RMII mode, FEC_TX_CLK is used as the REF_CLK, which is a 50 MHz ± 50 ppm continuous
reference clock. FEC_RX_DV is used as the CRS_DV in RMII. Other signals under RMII mode include
FEC_TX_EN, FEC_TXD[1:0], FEC_RXD[1:0] and FEC_RX_ER.
Figure 59
figure.
Freescale Semiconductor
M16
M17
M18
M19
M20
M21
ID
FEC_TXD[1:0] (output)
FEC_TX_EN
FEC_RXD[1:0]
FEC_RX_ER
REF_CLK(FEC_TX_CLK) pulse width high
REF_CLK(FEC_TX_CLK) pulse width low
REF_CLK to FEC_TXD[1:0], FEC_TX_EN invalid
REF_CLK to FEC_TXD[1:0], FEC_TX_EN valid
FEC_RXD[1:0], CRS_DV(FEC_RX_DV), FEC_RX_ER to REF_CLK setup
REF_CLK to FEC_RXD[1:0], FEC_RX_DV, FEC_RX_ER hold
REF_CLK (input)
shows RMII mode timings.
CRS_DV (input)
RMII Mode Timing
i.MX25 Applications Processor for Consumer and Industrial Products, Rev. 7
Figure 59. RMII Mode Signal Timing Diagram
Characteristic
Table 66
Table 66. RMII Signal Timing
M20
M18
describes the timing parameters (M16–M21) shown in the
M21
M19
M16
M17
35%
35%
Min.
—
3
2
2
Max.
65%
65%
12
—
—
—
REF_CLK period
REF_CLK period
Unit
ns
ns
ns
ns
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