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ISP1130

Universal Serial Bus compound hub with integrated keyboard controller

Philips Electronics 

Philips Semiconductors

ISP1130

USB compound hub with keyboard controller

6.1 80C51 microcontroller

An integrated 80C51 microcontroller serves as a keyboard controller. It has 8 kbytes

of mask ROM and 256 bytes of RAM. The I/O ports have been configured as an

8 × 18 line scan matrix. Three LED control outputs are available for keyboard status

indicators (Caps Lock, Num Lock and Scroll Lock). Interfacing to the USB hub is done

via 3 registers (command, data, status), which are accessible via the external data

memory address space (MOVX instruction).

The keyboard firmware resides in the ROM and enumerates the embedded function

as ‘HID compatible keyboard device’ during hub initialization.

The microcontroller runs on a 12 MHz clock, derived from the PLL oscillator. A

watchdog timer resets the microcontroller in case of a software hang-up.

6.2 Analog transceivers

The integrated transceivers interface directly to the USB cables through external

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. The slew rates

are adjusted according to the speed of the device connected and lie within the range

mentioned in the USB Specification Rev. 1.1.

6.3 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.

6.4 Hub repeater

The hub repeater is responsible for managing connectivity on a ‘per packet’ basis. It

implements ‘packet signalling’ and ‘resume’ connectivity. Low-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.

6.5 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.

6.6 General and individual port controller

The general and individual port controllers together 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.

9397 750 06895

Objective specification

Rev. 01 — 23 March 2000

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

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