Philips Semiconductors

PDIUSBD12

USB interface device with parallel bus

Product data

Rev. 08 — 20 December 2001

5 of 35

9397 750 09238

© Koninklijke Philips Electronics N.V. 2001. All rights reserved.

6.

Functional description

6.1 Analog transceiver

The integrated transceiver interfaces directly to the USB cables through termination

resistors.

6.2 Voltage regulator

A 3.3 V regulator is integrated on-chip to supply the analog transceiver. This voltage

is also provided as an output to connect to the external 1.5 k

Ω pull-up resistor.

Alternatively, the PDIUSBD12 provides SoftConnect technology with an integrated

1.5 k

Ω pull-up resistor.

6.3 PLL

A 6 MHz to 48 MHz clock multiplier PLL (Phase-Locked Loop) is integrated on-chip.

This allows for the use of a low-cost 6 MHz crystal. EMI is also minimized due to the

lower frequency crystal. No external components are needed for the operation of the

PLL.

6.4 Bit clock recovery

The bit clock recovery circuit recovers the clock from the incoming USB data stream

using 4

× oversampling principle. It is able to track jitter and frequency drift specified

by the USB specification.

6.5 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, and

handshake evaluation/generation.

6.6 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 PDIUSBD12, the 1.5 kΩ pull-up

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 performed without requiring to pull out the cable.

open-drain output of the DMA controller pin.