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Electrical Characteristics
MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
23-29
23.11 USB Interface AC Timing Specifications
lists USB interface timings.
NOTE
USB signals are sampled; setup and hold times are not normally required in
a transceiver connection.
Figure 23-22. USB Interface Timing
Table 23-22. USB Interface AC Timing Specifications
Name
Characteristic
48-66 MHz
Unit
Min
Max
US1
USB_CLK frequency of operation
1
1
USB_CLK accuracy should be +- 500ppm or better. USB_CLK may be stopped to conserve power.
48
48
MHz
US2
2
2
Specification values are not tested.
USB_CLK fall time (from V
h
= 2.4V to V
l
= 0.5V)
—
2
nS
US3
USB_CLK rise time (from V
l
= 0.5V to V
h
= 2.4V)
—
2
nS
US4
USB_CLK duty cycle (measured at 1.5 V)
45
55
%
US5
USB Inputs (USB_RP, USB_RN, USB_RxD) setup time to USB_CLK (rising)
6
—
nS
US6
USB Inputs (USB_RP, USB_RN, USB_RxD) hold time from USB_CLK (rising)
6
—
nS
US7
USB_CLK to USB outputs valid (USB_TP, USB_TN, USB_SUSP, USB_TxEN)
—
12
nS
US8
USB_CLK to USB outputs invalid (output hold) (USB_TP, USB_TN, USB_SUSP, USB_TxEN)
3
—
nS
USB_CLK
US1
US4a
US4b
US3
US2
V
h
V
l
(input)
US7
USB_TP
US8
US5
US6
USB_RP
USB_RN
USB_RxD
USB_TN
USB_SUSP
USB_TxEN