Group command, Group command write format, Addressing – Rainbow Electronics MAX34440 User Manual
Page 17: Alert and alert response address (ara), Addressing alert and alert response address (ara)
PMBus 6-Channel Power-Supply Manager
MAX34440
17
Group Command
The device supports the group command. With the
group command, a host can write different data to
multiple devices on the same serial bus with one long
continuous data stream. All the devices addressed dur-
ing this transaction wait for the host to issue a STOP
before beginning to respond to the command.
KEY:
S = START
Sr = REPEATED START
P = STOP
W = WRITE BIT (0)
A = ACKNOWLEDGE (0)
SHADED BLOCK = SLAVE TRANSACTION
Group Command Write Format
Addressing
The device responds to receiving its fixed slave address
by asserting an acknowledge (ACK) on the bus. The
device does not respond to a general call address; it
only responds when it receives its fixed slave address.
The only exception to this operation is if the ALERT
output is enabled (ALERT bit = 1 in MFR_MODE) and
ALERT has been asserted. When this condition occurs,
the device only recognizes the alert response address
(0001 100, 18h). See the ALERT and Alert Response
Address (ARA) section for more details.
ALERT and Alert Response Address (ARA)
If the ALERT output is enabled (ALERT bit = 1 in
MFR_MODE), when a fault occurs the device asserts the
ALERT signal and then waits for the host to send the alert
response address (ARA) as shown in the Alert Response
Address (ARA) Byte Format section. While waiting for
the ARA, the device does not respond to its fixed
slave address.
When the ARA is received and the device is asserting
ALERT, the device ACKs it and then attempts to place
its fixed slave address on the bus by arbitrating the
bus, since another device could also try to respond to
the ARA. The rules of arbitration state that the lowest
address device wins. If the device wins the arbitration,
it deasserts ALERT and begins to respond to its fixed
slave address. If the device loses arbitration, it keeps
ALERT asserted and waits for the host to once again
send the ARA.
SLAVE ADDRESS, COMMAND BYTE, AND DATA WORD FOR DEVICE 1
1
7
1
1
8
1
8
1
8
1
S
SLAVE
ADDRESS
W
A
COMMAND
CODE
A
DATA BYTE
LOW
A
DATA BYTE
HIGH
A
U
U U
SLAVE ADDRESS, COMMAND BYTE, AND DATA BYTE FOR DEVICE 2
1
7
1
1
8
1
8
1
Sr
SLAVE
ADDRESS
W
A
COMMAND
CODE
A
DATA BYTE
A
U
U U
SLAVE ADDRESS AND SEND BYTE FOR DEVICE 3
1
7
1
1
8
1
Sr
SLAVE
ADDRESS
W
A
COMMAND
CODE
A
U
U U
U
U U
SLAVE ADDRESS, COMMAND BYTE, AND DATA WORD FOR DEVICE N
1
7
1
1
8
1
8
1
8
1
1
Sr
SLAVE
ADDRESS
W
A
COMMAND
CODE
A
DATA BYTE
LOW
A
DATA BYTE
HIGH
A
P