DS80PCI800SQ Datasheet, PDF (22/45 Pages) Texas Instruments – DS80PCI800 2.5 Gbps / 5.0 Gbps / 8.0 Gbps 8 Channel PCI Express Repeater

DS80PCI800
SNLS334E – APRIL 2011 – REVISED MARCH 2012
AD[3:0] Settings
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
Table 8. Device Slave Address Bytes
Address Bytes (HEX)
B0
B2
B4
B6
B8
BA
BC
BE
C0
C2
C4
C6
C8
CA
CC
CE
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The SDA, SCL pins are 3.3V tolerant, but are not 5V tolerant. External pull-up resistor is required on the SDA.
The resistor value can be from 1 kΩ to 5 kΩ depending on the voltage, loading and speed. The SCL may also
require an external pull-up resistor and it depends on the Host that drives the bus.
TRANSFER OF DATA VIA THE SMBus
During normal operation the data on SDA must be stable during the time when SCL is High.
There are three unique states for the SMBus:
START: A High-to-Low transition on SDA while SCL is High indicates a message START condition.
STOP: A Low-to-High transition on SDA while SCL is High indicates a message STOP condition.
IDLE: If SCL and SDA are both High for a time exceeding t_BUF from the last detected STOP condition or if they
are High for a total exceeding the maximum specification for t_HIGH then the bus will transfer to the IDLE state.
SMBus TRANSACTIONS
The device supports WRITE and READ transactions. See Register Description table for register address, type
(Read/Write, Read Only), default value and function information.
WRITING A REGISTER
To write a register, the following protocol is used (see SMBus 2.0 specification).
1. The Host drives a START condition, the 7-bit SMBus address, and a “0” indicating a WRITE.
2. The Device (Slave) drives the ACK bit (“0”).
3. The Host drives the 8-bit Register Address.
4. The Device drives an ACK bit (“0”).
5. The Host drive the 8-bit data byte.
6. The Device drives an ACK bit (“0”).
7. The Host drives a STOP condition.
The WRITE transaction is completed, the bus goes IDLE and communication with other SMBus devices may
now occur.
READING A REGISTER
To read a register, the following protocol is used (see SMBus 2.0 specification).
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