max5952auaxt Maxim Integrated Products, Inc., max5952auaxt Datasheet - Page 25

• Manufacturer Part Number: max5952auaxt
• Description: Max5952 High-power, Quad, Pse Controller For Power-over-ethernet
• Manufacturer: Maxim Integrated Products, Inc.

The MAX5952 reads using the MAX5952’s internally
stored command byte as an address pointer, the same
way the stored command byte is used as an address
pointer for a write. The pointer auto-increments after
reading each data byte using the same rules as for a
write. Thus, a read is initiated by first configuring the
MAX5952’s command byte by performing a write (Figure
11). The master now reads ‘n’ consecutive bytes from
the MAX5952, with the first data byte read from the regis-
ter addressed by the initialized command byte (Figure
12). When performing read-after-write verification,
remember to reset the command byte’s address
because the stored control byte address auto-incre-
ments after the write.
When the MAX5952 operates on a 2-wire interface with
multiple masters, a master reading the MAX5952
should use repeated starts between the write which
sets the MAX5952’s address pointer, and the read(s)
that take the data from the location(s). It is possible for
master 2 to take over the bus after master 1 has set up
Figure 11. Control and Single Data Byte Received
Figure 12. ‘n’ Data Bytes Received
S
S
HOW CONTROL BYTE AND DATA BYTE MAP
HOW CONTROL BYTE AND DATA BYTE MAP
SLAVE ADDRESS
SLAVE ADDRESS
ACKNOWLEDGE FROM MAX5952
ACKNOWLEDGE FROM MAX5952
______________________________________________________________________________________
Operation with Multiple Masters
INTO THE REGISTER
INTO THE REGISTER
Message Format for Reading
R/W
R/W
0
0
High-Power, Quad, PSE Controller
A
A
D15 D14 D13 D12 D11 D10
D15 D14 D13 D12 D11 D10
CONTROL BYTE
CONTROL BYTE
ACKNOWLEDGE FROM MAX5952
ACKNOWLEDGE FROM MAX5952
for Power-Over-Ethernet
the MAX5952’s address pointer but before master 1
has read the data. If master 2 subsequently resets the
MAX5952’s address pointer then master 1’s read may
be from an unexpected location.
Address auto-incrementing allows the MAX5952 to be
configured with fewer transmissions by minimizing the
number of times the command address needs to be
sent. The command address stored in the MAX5952
generally increments after each data byte is written or
read (Table 5). The MAX5952 is designed to prevent
overwrites on unavailable register addresses and unin-
tentional wrap-around of addresses.
Table 5. Auto-Increment Rules
ADDRESS RANGE
COMMAND BYTE
D9
D9
0x00 to 0x26
D8
0x26
D8
A
A
Command Address Auto-Incrementing
D7
D7
D6
D6
Command address auto-increments
after byte read or written
Command address remains at 0x26
after byte written or read
D5
AUTO-INCREMENT BEHAVIOR
D5
ACKNOWLEDGE FROM MAX5952
ACKNOWLEDGE FROM MAX5952
DATA BYTE
DATA BYTE
D4
D4
n BYTES
1 BYTE
D3
D3
D2
D2
MEMORY WORD ADDRESS
MEMORY WORD ADDRESS
D1
D1
AUTO-INCREMENT
AUTO-INCREMENT
D0
D0
A
A
P
P
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