DS125BR401SQ Datasheet, PDF (15/52 Pages) Texas Instruments – Low-Power 12.5-Gbps 4-Lane Repeater With Input Equalization and Output De-Emphasis

DS125BR401
www.ti.com
SNLS419C – JULY 2012 – REVISED APRIL 2013
SMBUS Master Mode
The DS125BR401 device supports reading directly from an external EEPROM device by implementing SMBus
Master mode. When using the SMBus master mode, the DS125BR401 will read directly from specific location in
the external EEPROM. When designing a system for using the external EEPROM, the user needs to follow these
specific guidelines.
• Set ENSMB = Float — enable the SMBUS master mode.
• The external EEPROM device address byte must be 0xA0'h and capable of 400 kHz operation at 2.5V and
3.3V supply.
• Set the AD[3:0] inputs for SMBus address byte. When the AD[3:0] = 0000'b, the device address byte is B0'h.
When tying multiple DS125BR401 devices to the SDA and SCL bus, use these guidelines to configure the
devices.
• Use SMBus AD[3:0] address bits so that each device can loaded it's configuration from the EEPROM.
Example below is for 4 device.
– U1: AD[3:0] = 0000 = 0xB0'h,
– U2: AD[3:0] = 0001 = 0xB2'h,
– U3: AD[3:0] = 0010 = 0xB4'h,
– U4: AD[3:0] = 0011 = 0xB6'h
• Use a pull-up resistor on SDA and SCL; value = 2k ohms
• Daisy-chain READEN# (pin 26) and ALL_DONE# (pin 27) from one device to the next device in the sequence
so that they do not compete for the EEPROM at the same time.
1. Tie READEN# of the 1st device in the chain (U1) to GND
2. Tie ALL_DONE# of U1 to READEN# of U2
3. Tie ALL_DONE# of U2 to READEN# of U3
4. Tie ALL_DONE# of U3 to READEN# of U4
5. Optional: Tie ALL_DONE# output of U4 to a LED to show the devices have been loaded successfully
Below is an example of a 2 kbits (256 x 8-bit) EEPROM in hex format for the DS125BR401 device. The first 3
bytes of the EEPROM always contain a header common and necessary to control initialization of all devices
connected to the I2C bus. CRC enable flag to enable/disable CRC checking. If CRC checking is disabled, a fixed
pattern (8’hA5) is written/read instead of the CRC byte from the CRC location, to simplify the control. There is a
MAP bit to flag the presence of an address map that specifies the configuration data start in the EEPROM. If the
MAP bit is not present the configuration data start address is derived from the DS125BR401 address and the
configuration data size. A bit to indicate an EEPROM size > 256 bytes is necessary to properly address the
EEPROM. There are 37 bytes of data size for each DS125BR401 device.
:2000000000001000000407002FAD4002FAD4002FAD4002FAD401805F5A8005F5A8005F5AD8
:200020008005F5A800005454000000000000000000000000000000000000000000000000F6
:20006000000000000000000000000000000000000000000000000000000000000000000080
:20008000000000000000000000000000000000000000000000000000000000000000000060
:2000A000000000000000000000000000000000000000000000000000000000000000000040
:2000C000000000000000000000000000000000000000000000000000000000000000000020
:2000E000000000000000000000000000000000000000000000000000000000000000000000
:200040000000000000000000000000000000000000000000000000000000000000000000A0
Copyright © 2012–2013, Texas Instruments Incorporated
Product Folder Links: DS125BR401
Submit Documentation Feedback
15