mpc880 Freescale Semiconductor, Inc, mpc880 Datasheet - Page 72

• Manufacturer Part Number: mpc880
• Description: Mpc885 Powerquicc Integrated Communications Processor
• Manufacturer: Freescale Semiconductor, Inc

FEC Electrical Characteristics
Figure 73
15.2
The transmitter functions correctly up to a MII_TX_CLK maximum frequency of 25 MHz + 1%. The
RMII transmitter functions correctly up to a RMII_REFCLK maximum frequency of 50 MHz + 1%.
There is no minimum frequency requirement. In addition, the processor clock frequency must exceed the
MII_TX_CLK frequency
Table 35
72
M20_RMII
M21_RMII
Num
M5
M6
M7
M8
provides information on the MII and RMII transmit signal timing.
MII_RXD[3:0] (Inputs)
MII and Reduced MII Transmit Signal Timing
shows MII receive signal timing.
MII_RX_CLK (Input)
MII_TX_CLK to MII_TXD[3:0], MII_TX_EN, MII_TX_ER invalid
MII_TX_CLK to MII_TXD[3:0], MII_TX_EN, MII_TX_ER valid
RMII_TXD[1:0], RMII_TX_EN to RMII_REFCLK setup
RMII_TXD[1:0], RMII_TX_EN data hold from RMII_REFCLK rising
edge
MII_TX_CLK and RMII_REFCLK pulse width high
MII_TX_CLK and RMII_REFCLK pulse width low
MII_RX_ER
MII_RX_DV
MPC885/MPC880 PowerQUICC™ Hardware Specifications, Rev. 4
–
1%.
Figure 73. MII Receive Signal Timing Diagram
Table 35. MII Transmit Signal Timing
Characteristic
M1
M2
M3
M4
35%
35%
Min
—
5
4
2
Max
65%
65%
25
—
—
—
Freescale Semiconductor
MII_TX_CLK or
MII_TX_CLK or
RMII_REFCLK
RMII_REFCLK
period
period
Unit
ns
ns
ns
ns