PDIUSBH12 datasheet(4/28 Pages) PHILIPS

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Philips Semiconductors

Product specification

PDIUSBH12

USB 2-port hub

1999 Jul 22

Analog Transceivers

These transceivers interface directly to the USB cables through

some termination resistors. They are capable of transmitting and

receiving serial data at both “full speed” (12 Mbit/s) and “low speed”

(1.5 Mbit/s) data rates.

Hub Repeater

The hub repeater is responsible for managing connectivity on a per

packet basis. It implements packet signaling connectivity and

resume connectivity.

Low speed devices can be connected to downstream ports since the

repeater will not propagate upstream packets to downstream ports,

to which low speed devices are connected, unless they are

preceded by a PREAMBLE PID.

End of Frame Timers

This block contains the specified EOF1 and EOF2 timers which are

used to detect loss-of-activity and babble error conditions in the hub

repeater. The timers also maintain the low-speed keep-alive strobe

which is sent at the beginning of a frame.

General and Individual Port Controller

The general and individual port controllers together provide status

and control of individual downstream ports. Via the I2C-interface a

microcontroller can access the downstream ports and request or

change the status of each individual port.

Any change in the status or settings of the individual port will result

in an interrupt request. Via an interrupt register, the servicing

microcontroller can look up the downstream port which generated

the interrupt and request its new status. Any port status change can

then be reported to the host via the hub status change (interrupt)

endpoint.

PLL

A 12 MHz to 48 MHz clock multiplier PLL (Phase-Locked Loop) is

integrated on-chip. This allows for the use of low-cost 12 MHz

crystal. EMI is also minimized due to lower frequency crystal. No

external components are needed for the operation of the PLL.

Bit Clock Recovery

The bit clock recovery circuit recovers the clock from the incoming

USB data stream using 4X over-sampling principle. It is able to track

jitter and frequency drift specified by the USB specification.

Philips Serial Interface Engine (PSIE)

The Philips SIE implements the full USB protocol layer. It is

completely hardwired for speed and needs no firmware intervention.

The functions of this block include: synchronization pattern

recognition, parallel/serial conversion, bit stuffing/de-stuffing, CRC

checking/generation, PID verification/generation, address

recognition, handshake evaluation/generation.

Memory Management Unit (MMU) and Integrated

RAM

The MMU and the integrated RAM is used to handle the large

difference in data rate between USB, running in bursts of 12 Mbit/s

and the I2C interface to the microcontroller, running at up to

1 Mbit/s. This allows the microcontroller to read and write USB

packets at its own speed through I2C.

I2C Slave Interface

This block implements the necessary I2C interface protocol. A slave

I2C allows for simple micro-coding. An interrupt is used to alert the

microcontroller whenever the PDIUSBH12 needs attention. As a

slave I2C device, the PDIUSBH12 I2C clock: SCL is an input and is

controlled by the microcontroller. The I2C interface can run up to 1

Mbit/s.

SoftConnect

™

The connection to the USB is accomplished by bringing D+ (for

high-speed USB device) high through a 1.5 k

Ω pull-up resistor. In

the PDIUSBH12, the 1.5 k

Ω pull-up resistor is integrated on-chip

and is not connected to VCC by default. Similarly, the 15 kΩ

pull-down resistors are integrated on-chip and are not connected to

GND by default. The connection of the internal resistors to Vcc is

established through a command sent by the external/system

microcontroller. This allows the system microcontroller to complete

its initialization sequence before deciding to establish connection to

the USB. Re-initialization of the USB bus connection can also be

affected without requiring the pull out of the cable.

The PDIUSBH12 will check for USB VBUS availability before the

connection can be established. VBUS sensing is provided through

OCURRENT_N pin. See the pin description for details. Sharing of

VBUS sensing and overcurrent sensing can be easily accomplished

by using VBUS voltage as the pull-up voltage for the open drain

output of the overcurrent indication device.

It should be noted that the tolerance of the internal resistors is

higher (30%) than that specified by the USB specification (5%).

However, the overall VSE voltage specification for the connection

can still be met with good margin. The decision to make use of this

feature lies with the users.

SoftConnect

™ is a patent pending technology from Philips

Semiconductors.

GoodLink

™

Good downstream USB connection indication is provided through

GoodLink™ technology. When the port is enabled and there is at

least one valid upstream traffic from the port, the LED indicator will

be ON. The LED indicator will blink on every valid upstream traffic. A

valid upstream traffic is defined as traffic with a good SOP and

terminated by a good EOP. During global suspend, all LEDs will be

OFF.

This feature provides a user-friendly indicator on the status of the

hub, the connected downstream devices and the USB traffic. It is a

useful field diagnostics tool to isolate the faulty equipment. This

feature helps lower the field support and the hotline costs.

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