mcs7717 MosChip, mcs7717 Datasheet - Page 7

• Manufacturer Part Number: mcs7717
• Description: Three Port Usb Hub With 1 Serial, 1 Printer
• Manufacturer: MosChip

MCS7717
Three Port USB Hub with 1 Serial, 1 Printer
USB Description
Analog Transceivers
The on-chip transceivers are connected directly to USB cables through external series resistors. They
transmit and receive serial data at both full-speed (12Mbit/s) and low-speed (1.5Mbit/s) data rates. Slew rates
are automatically adjusted according to the speed of the device connected and lie within the range defined in
the USB Specification Rev. 1.1.
Serial Interface Engine
This engine implements the complete USB protocol layer including: parallel /serial conversion,
synchronization pattern recognition, CRC checking/generation, bit (de)stuffing, packet identifier (PID)
verification/generation, address recognition and handshake evaluation/generation.
Bit Clock Recovery
The bit clock recovery circuit recovers the clock from the incoming USB data stream using 4x over sampling.
It is able to track in the presence of jitter and frequency drift as specified by the USB Specification Rev. 1.1.
3.3V Source
A 5V to 3.3V DC-DC regulator is integral to the chip relieving the need for a +3.3V source. It supplies the
analog transceivers and internal logic and can be used to supply the 1.5kΩ pull-up resistor on the DP line of
the upstream connection.
PLL Clock Multiplier
An integral Phase-Locked Loop (PLL) performs 6 to 48MHz clock multiplication and requires no external
components except the crystal. This allows for the use of low-cost 6MHz crystals which reduce high
frequency radiated Electro-Magnetic Interference (EMI).
Downstream Ports
Low and High-Speed devices can be connected to downstream ports. If a Low-Speed device is detected,
the repeater will not propagate upstream packets to the corresponding port, unless they are preceded by a
PREAMBLE PID.
Two timers (EOF1 and EOF2) are used to detect “loss-of-activity” and “babble” error conditions in the hub
repeater. They also maintain the Low-Speed keep-alive strobe that is sent at the beginning of a frame.
General and individual port controllers provide status and control of individual downstream ports. Any port
status change will be reported to the host via the Hub Status Change (interrupt) endpoint.
Link Status Indication
Indication of a good USB connection is provided by an LED directly connected via an external 330Ω resistor
(using nUSBnPWR), see pin listing.
Rev. 1.7
Page 7