mpc880 Freescale Semiconductor, Inc, mpc880 Datasheet - Page 71

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

14 USB Electrical Characteristics
This section provides the AC timings for the USB interface.
14.1
The USB Port uses the transmit clock on SCC1.
1
15 FEC Electrical Characteristics
This section provides the AC electrical specifications for the fast Ethernet controller (FEC). Note that the
timing specifications for the MII signals are independent of system clock frequency (part speed
designation). Also, MII signals use TTL signal levels compatible with devices operating at either 5.0 or
3.3 V.
15.1
The receiver functions correctly up to a MII_RX_CLK maximum frequency of 25 MHz + 1%. The
reduced MII (RMII) receiver 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_RX_CLK frequency
Table 34
Freescale Semiconductor
M1_RMII
M2_RMII
Name
USBCLK accuracy should be ±500 ppm or better. USBCLK may be stopped to conserve power.
US1
US4
Num
M1
M2
M3
M4
provides information on the MII and RMII receive signal timing.
USBCLK frequency of operation
Low speed
Full speed
USBCLK duty cycle (measured at 1.5 V)
USB Interface AC Timing Specifications
MII and Reduced MII Receive Signal Timing
MII_RX_CLK pulse width high
MII_RX_CLK pulse width low
setup
RMII_REFCLK to RMII_RXD[1:0], RMII_CRS_DV, RMII_RX_ERR
hold
MII_RXD[3:0], MII_RX_DV, MII_RX_ERR to MII_RX_CLK setup
MII_RX_CLK to MII_RXD[3:0], MII_RX_DV, MII_RX_ER hold
RMII_RXD[1:0], RMII_CRS_DV, RMII_RX_ERR to RMII_REFCLK
MPC885/MPC880 PowerQUICC™ Hardware Specifications, Rev. 4
Table 33. USB Interface AC Timing Specifications
Characteristic
Table 34. MII Receive Signal Timing
1
Characteristic
–
1%.
Table 33
lists the USB interface timings.
35%
35%
Min
5
5
4
2
Max
65%
65%
—
—
—
—
USB Electrical Characteristics
All Frequencies
Min
45
MII_RX_CLK period
MII_RX_CLK period
48
6
Max
Unit
55
ns
ns
ns
ns
MHz
MHz
Unit
%
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