Datasheet

DS80PCI800
SNLS334E –APRIL 2011–REVISED MARCH 2012 www.ti.com
Table 8. Device Slave Address Bytes
AD[3:0] Settings Address Bytes (HEX)
0000 B0
0001 B2
0010 B4
0011 B6
0100 B8
0101 BA
0110 BC
0111 BE
1000 C0
1001 C2
1010 C4
1011 C6
1100 C8
1101 CA
1110 CC
1111 CE
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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