USB2503-HZH Standard Microsystems Corp., USB2503-HZH Datasheet - Page 23

• Manufacturer Part Number: USB2503-HZH
• Description: Interface, Integrated USB2.0 Compatible 3-Port Hub
• Manufacturer: Standard Microsystems Corp.

Integrated USB2.0 Compatible 3-Port Hub
Datasheet
SMSC USB2503
5.3.1
5.3.1.1
Field:
Bits:
Start
SMBus interface, external EEPROM support is no longer available (and the user-defined descriptor
data must be downloaded via the SMBus). Due to system issues, the SMSC Hub waits indefinitely for
the SMBus code load to complete and only “appears” as a newly connected device on USB after the
code load is complete.
The Hub’s SMBus implementation is a subset of the SMBus interface to the host. The device is a
slave-only SMBus device. The implementation in the device is a subset of SMBus since it only supports
two protocols.
The Write Byte and Read Byte protocols are the only valid SMBus protocols for the Hub. The Hub
responds to other protocols as described in
page
The SMBus interface is used to read and write the registers in the device. The register set is shown
in
Bus Protocols
Typical Write Byte and Read Byte protocols are shown below. Register accesses are performed using
7-bit slave addressing, an 8-bit register address field, and an 8-bit data field. The shading indicates
the Hub driving data on the SMBDATA line; otherwise, host data is on the SDA/SMBDATA line.
The slave address is the unique SMBus Interface Address for the Hub that identifies it on SMBus. The
register address field is the internal address of the register to be accessed. The register data field is
the data that the host is attempting to write to the register or the contents of the register that the host
is attempting to read.
Note: Data bytes are transferred MSB first (msb first).
Byte Protocols
When using the Hub SMBus Interface for byte transfers, a write will always consist of the SMBus
Interface Slave Address byte, followed by the Internal Address Register byte, then the data byte.
The normal read protocol consists of a write to the HUB with the SMBus Interface Address byte,
followed by the Internal Address Register byte. Then restart the Serial Communication with a Read
consisting of the SMBus Interface Address byte, followed by the data byte read from the Hub. This
can be accomplished by using the Read Byte protocol.
Note: For the following SMBus tables:
Write Byte
The Write Byte protocol is used to write data to the registers. The data will only be written if the protocol
shown in
protocol.
Read Byte
The Read Byte protocol is used to read data from the registers. The data will only be read if the
protocol shown in
Byte protocol.
1
Denotes Master-to-Slave
Section 5.3.9, "Internal SMBus Memory Register Set," on page
19. Reference the System Management Bus Specification, Rev 1.0.
Slave Addr
Table 5.2
7
Table 5.3
is performed correctly. Only one byte is transferred at a time for a Write Byte
Table 5.2 SMBus Write Byte Protocol
Wr
1
is performed correctly. Only one byte is transferred at a time for a Read
Ack
1
18
Reg. Addr
Denotes Slave-to-Master
Section 5.3.2, "Invalid Protocol Response Behavior," on
8
Ack
1
19.
Reg. Data
8
Revision 1.3 (08-24-04)
Ack
1
Stop
1