Datasheet

LTC3880/LTC3880-1
29
3880fc
For more information www.linear.com/LTC3880
OPERATION
A value shown below a field in the following figures is a
mandatory value for that field.
The data formats implemented by PMBus are:
n
Master transmitter transmits to slave receiver. The
transfer direction in this case is not changed.
n
Master reads slave immediately after the first byte. At
the moment of the first acknowledgment (provided by
the slave receiver) the master transmitter becomes a
master receiver and the slave receiver becomes a slave
transmitter.
n
Combined format. During a change of direction within
a transfer, the master repeats both a start condition and
the slave address but with the R/W bit reversed. In this
case, the master receiver terminates the transfer by
generating a NACK on the last byte of the transfer and
a STOP condition.
Examples of these formats are shown in Figures 7-16.
Figure 5. Timing Diagram
Figure 6. PMBus Packet Protocol Diagram Element Key
SDA
SCL
t
HD(STA)
t
HD(DAT)
t
SU(STA)
t
SU(STO)
t
SU(DAT)
t
LOW
t
HD(SDA)
t
SP
t
BUF
START
CONDITION
STOP
CONDITION
REPEATED START
CONDITION
START
CONDITION
t
r
t
f
t
r
t
f
t
HIGH
3880 F05
SLAVE ADDRESS DATA BYTEWr A A P
3880 F06
S
7
S START CONDITION
Sr REPEATED START CONDITION
Rd READ (BIT VALUE OF 1)
Wr WRITE (BIT VALUE OF 0)
x SHOWN UNDER A FIELD INDICATES THAT THAT
FIELD IS REQUIRED TO HAVE THE VALUE OF x
A ACKNOWLEDGE (THIS BIT POSITION MAY BE 0
FOR AN ACK OR 1 FOR A NACK)
P STOP CONDITION
PEC PACKET ERROR CODE
MASTER TO SLAVE
SLAVE TO MASTER
CONTINUATION OF PROTOCOL
81 1 1
x x
11
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