MAX5980 MAXIM [Maxim Integrated Products], MAX5980 Datasheet - Page 25

• Manufacturer Part Number: MAX5980
• Description: Quad, IEEE 802.3at/af PSE Controller
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 13. Read Format, Control, and n Data Bytes Read
Figure 12. Write Format, Control, and n Data Bytes Written
Figure 11. Write Format, Control, and Single Data Byte Written
A read command for the device comprises the device
slave address transmission with the R/W bit set to 1, fol-
lowed by at least 1 byte of information. As with a write
command, the first byte of information is the command
byte. The device then reads using the internally stored
command byte as an address pointer, the same way the
stored command byte is used as an address pointer for
S
S
S
CONTROL BYTE STORED ON STOP CONDITION
CONTROL BYTE STORED ON STOP CONDITION
CONTROL BYTE STORED ON STOP CONDITION
ACKNOWLEDGE FROM THE MAX5980
ACKNOWLEDGE FROM THE MAX5980
ACKNOWLEDGE FROM THE MAX5980
SLAVE ADDRESS
SLAVE ADDRESS
SLAVE ADDRESS
Message Format for Reading
Quad, IEEE 802.3at/af PSE Controller
R/W
R/W
R/W
1
0
0
ACK
ACK
ACK
CB7 CB6 CB5 CB4 CB3 CB2 CB1 CB0
CB7
CB7 CB6 CB5 CB4 CB3 CB2 CB1 CB0
CB6 CB5 CB4 CB3 CB2 CB1 CB0
ACKNOWLEDGE FROM THE MAX5980
CONTROL BYTE
CONTROL BYTE
CONTROL BYTE
for Power-over-Ethernet
a write. This pointer autoincrements after reading each
data byte using the same rules as for a write, though the
master now sends the acknowledge bit after each read
receipt (Figure 13). When performing read-after-write
verification, remember to reset the command byte’s
address because the stored control byte address auto-
increments after the write.
ACK
ACK
ACK
D7
D7
D7
ACKNOWLEDGE/NACK FROM THE MASTER
ACKNOWLEDGE FROM THE MAX5980
D6
ACKNOWLEDGE FROM THE MAX5980
D6
D6
WORD ADDRESS AUTOINCREMENT
WORD ADDRESS AUTOINCREMENT
WORD ADDRESS AUTOINCREMENT
D5
D5
DATA BYTE (n BYTES)
REPEAT FOR n BYTES (ACK)
D5
DATA BYTE (n BYTES)
DATA BYTE (1 BYTE)
REPEAT FOR n BYTES
D4
D4
D4
D3
D3
D3
D2
D2
D2
D1
D1
D1
D0
D0
D0
NACK
ACK/
ACK
ACK
(NACK)
P
P
P
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