68HC705JB4 datasheet(78/134 Pages) FREESCALE

78 / 134 page

GENERAL RELEASE SPECIFICATION

February 24, 1999

MOTOROLA

UNIVERSAL SERIAL BUS MODULE

MC68HC05JB4

10-12

REV 2

with respect to local ground reference without damage.

10.4.2.2 Low Speed (1.5 Mbs) Driver Characteristics

The rise and fall time of the signals on this cable are greater than 75 ns to keep

RFI emissions under FCC class B limits, and less than 300 ns to limit timing

delays and signaling skews and distortions. The driver reaches the speciﬁed static

signal levels with smooth rise and fall times, and minimal reﬂections and ringing

when driving the cable. This driver is used only on network segments between low

speed devices and the ports to which they are connected.

Figure 10-12. Low Speed Driver Signal Waveforms

10.4.3 Receiver Characteristics

USB data transmission is done with differential signals. A differential input receiver

is used to accept the USB data signal. A differential 1 on the bus is represented by

D+ being at least 200 mV more positive than D– as seen at the receiver, and a

differential 0 is represented by D– being at least 200 mV more positive than D+ as

seen at the receiver. The signal cross over point must be between 1.3V and 2.0V.

The receiver features an input sensitivity of 200 mV when both differential data

inputs are in the range of 0.8 V to 2.5 V with respect to the local ground reference.

This is called the common mode input voltage range. Proper data reception is also

achieved when the differential data lines are outside the common mode range, as

shown in Figure 10-13. The receiver can tolerate static input voltages between

–0.5V to 3.8 V with respect to its local ground reference without damage. In

addition to the differential receiver, there is a single-ended receiver (schmitt

trigger) for each of the two data lines.

ONE BIT

TIME

(1.5 Mb/s)

SIGNAL PINS

PASS OUTPUT SPEC

LEVELS WITH MINIMAL

REFLECTIONS AND RINGING

VSE (min)

VSE (max)

VSS

Freescale Semiconductor, Inc.

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68HC705JB4 Datasheet(PDF) 78 Page - Freescale Semiconductor, Inc

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