PDIUSBH11 Datasheet, PDF (6/26 Pages) NXP Semiconductors – Universal Serial Bus Hub

Philips Semiconductors
Universal Serial Bus Hub
Product specification
PDIUSBH11
APPLICATION DIAGRAM
3.3V
USB
UPSTREAM
H11
48MHz
12MHz
I²C
µC
USB
5V
DOWNSTREAM
POWER SWITCH
AND
OVERCURRENT CIRCUIT
SWITCHED
5V
ENABLE LED
I²C Interface.
The I²C bus is used to interface to an external microcontroller
needed to control the operation of the hub. For cost consideration,
the target system microcontroller can be shared and utilized for this
purpose. The PDIUSBH11 implements a slave I²C interface. When
the PDIUSBH11 needs to communicate with the microcontroller it
asserts an interrupt signal. The microcontroller services this
interrupt by reading the appropriate status register on the
PDIUSBH11 through the I²C bus. (For more information about the
I²C serial bus, refer to the I²C handbook, Philips order number 9397
750 00013).
The I²C interface on the PDIUSBH11 defines two types of
transactions :
1. command transaction
A command transaction is used to define which data (e.g., status
byte, buffer data, ...) will be read from / written to the USB
interface in the next data transaction. A data transaction usually
follows a command transaction.
2. data transaction
A data transaction reads data from / writes data to the USB
interface. The meaning of the data is dependent on the
command transaction which was sent before the data
transaction.
Two addresses are used to differentiate between command and
data transactions. Writing to the command address is interpreted as
a command, while reading from / writing to the data address is used
to transfer data between the PDIUSBH11 and the controller.
ADDRESS TABLE
TYPE OF ADDRESS
Command
Data
PHYSICAL ADDRESS
(MSB to LSB)
0011 011 (binary)
0011 010 (binary)
SV00227
Protocol
An I²C transaction starts with a ‘Start Condition’, followed by an
address. When the address matches either the command or data
address the transaction starts and runs until a ‘Stop Condition’ or
another ‘Start Condition’ (repeated start) occurs.
The command address is write-only and is unable to do a read. The
next bytes in the message are interpreted as commands. Several
command bytes can be sent after one command address. Each of
the command bytes is acknowledged and passed on to the Memory
Management Unit inside the PDIUSBH11.
When the start condition address matches the data address, the
next bytes are interpreted as data. When the RW bit in the address
indicates a ‘master writes data to slave’ (=‘0’) the bytes are received,
acknowledged and passed on to the Memory Management Unit. If
the RW bit in the address indicates a ‘master reads data from slave’
(=‘1’) the PDIUSBH11 will send data to the master. The I²C-master
must acknowledge all data bytes except the last one. In this way the
I²C interface knows when the last byte has been transmitted and it
then releases the SDA line so that the master controller can
generate the STOP condition.
Repeated start support allows another packet to be sent without
generating a Stop Condition.
Timing
When the master writes data to the PDIUSBH11, the data is
sampled 1 micro-second after the rising edge of SCL. When the
PDIUSBH11 writes data to the master, the data is driven 1
micro-second after the falling edge of SCL.
1997 Aug 01
6