max5952auaxt Maxim Integrated Products, Inc., max5952auaxt Datasheet - Page 37

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

Enable the SMODE function (Table 25) by setting
EN_WHDOG (R1Fh[7]) to 1. SMODE_ bit goes high
when the watchdog counter reaches zero and the
port(s) switch over to hardware-controlled mode.
Set EN_WHDOG (R1Fh[7]) to 1 to enable the watchdog
function. When activated, the watchdog timer counter,
WDTIME[7:0], continuously decrements toward zero
once every 164ms. Once the counter reaches zero
(also called watchdog expiry), the MAX5952 enters
hardware-controlled mode and each port shifts to a
mode set by the HWMODE_ bit in register R1Fh (Table
27). Use software to set WDTIME (Table 26) and contin-
uously set this register to some nonzero value before
Table 25. SMODE Enable Register
Table 26. Watchdog Register
SMODE4
SMODE3
SMODE2
SMODE1
WDTIME
SYMBOL
SYMBOL
ADDRESS = 1Ch
ADDRESS = 1Eh
______________________________________________________________________________________
BIT
BIT
7
6
5
4
3
2
1
0
3
2
1
0
CoR
CoR
CoR
CoR
CoR
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
High-Power, Quad, PSE Controller
Port 4 hardware control flag
Port 3 hardware control flag
Port 2 hardware control flag
Port 1 hardware control flag
WDTIME[7]
WDTIME[6]
WDTIME[5]
WDTIME[4]
WDTIME[3]
WDTIME[2]
WDTIME[1]
WDTIME[0]
for Power-Over-Ethernet
SMODE_ also goes high each and every time the soft-
ware tries to power on a port, but is denied since the
port is in hardware mode. A reset sets R1Ch = 00h.
the register reaches zero to prevent a watchdog expiry.
In this way, the software gracefully manages the power
to ports upon a system crash or switchover.
While in hardware-controlled mode, the MAX5952
ignores all requests to turn the power on and the flag
SMODE_ indicates that the hardware has taken control
of the MAX5952 operation. In addition, the software is
not allowed to change the mode of operation in hard-
ware-controlled mode. A reset sets R1Eh = 00h.
DESCRIPTION
DESCRIPTION
37