ISP1181 데이터 시트보기 (PDF) - Philips Electronics

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ISP1181

Full-speed Universal Serial Bus interface device

Philips Electronics 

Philips Semiconductors

ISP1181

Full-speed USB interface

7.2 Philips Serial Interface Engine (SIE)

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 (de-)stuffing, CRC

checking/generation, Packet IDentifier (PID) verification/generation, address

recognition, handshake evaluation/generation.

7.3 Memory Management Unit (MMU) and integrated RAM

The MMU and the integrated RAM provide the conversion between the USB speed

(12 Mbit/s bursts) and the parallel interface to the microcontroller (max. 12 Mbyte/s).

This allows the microcontroller to read and write USB packets at its own speed.

7.4 SoftConnect

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

devices) HIGH through a 1.5 kΩ pull-up resistor. In the ISP1181 the 1.5 kΩ pull-up

resistor is integrated on-chip and is not connected to VCC by default. The connection

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 with the USB. Re-initialization of the USB connection

can also be performed without disconnecting the cable.

The ISP1181 will check for USB VBUS availability before the connection can be

established. VBUS sensing is provided through pin VBUS.

Remark: Note that the tolerance of the internal resistors is 25%. This is higher than

the 5% tolerance specified by the USB specification. However, the overall VSE voltage

specification for the connection can still be met with a good margin. The decision to

make use of this feature lies with the USB equipment designer.

7.5 GoodLink

Indication of a good USB connection is provided at pin GL through GoodLink

technology. During enumeration the LED indicator will blink on momentarily. When

the ISP1181 has been successfully enumerated (the device address is set), the LED

indicator will remain permanently on. Upon each successful packet transfer (with

ACK) to and from the ISP1181 the LED will blink off for 100 ms. During ‘suspend’

state the LED will remain off.

This feature provides a user-friendly indicator of the status of the USB device, the

connected hub and the USB traffic. It is a useful field diagnostics tool for isolating

faulty equipment. It can therefor help to reduce field support and hotline overhead.

A register bit can be set to stop the GoodLink LED blinking in traffic (see Table 20).

The LED indicator will then be permanently on.

7.6 Bit clock recovery

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

using a 4× over-sampling principle. It is able to track jitter and frequency drift as

specified by the USB Specification Rev. 1.1.

9397 750 06896

Objective specification

Rev. 01 — 13 March 2000

© Philips Electronics N.V. 2000. All rights reserved.

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