Rainbow-electronics MAX5945 Manual do Utilizador descarregar pdf (Página 31)

Writing a 1 to CLR_INT (Table 22) clears all the event

registers and the corresponding interrupt bits in register

R00h. Writing a 1 to RESET_P_ turns off power to the cor-

responding port and resets only the status and event

registers of that port. After execution, the bits reset to 0.

Writing a 1 to RESET_IC causes a global software reset,

after which the register map is set back to its reset state.

A reset sets R1Ah = 00h.

Enable SMODE function (Table 24) 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. SMODE_ also

goes high each and every time the software tries to

power-on a port but is denied since the port is in hard-

ware mode. A reset sets R1Ch = 00h.

Set EN_WHDOG (R1Fh[7]) to 1 (Table 25) 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 MAX5945 enters hard-

ware-controlled mode and each port shifts to a mode set

by the HWMODE_ bit in register R1Fh (Table 24). Use

software to set WDTIME and continuously set this register

to some non-zero value before 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 MAX5945

ignores all requests to turn the power on and the flag

SMODE_ indicates that the hardware took control of the

MAX5945 operation. In addition, the software is not

allowed to change the mode of operation in hardware-

controlled mode. A reset sets R1Eh = 00h.

Setting EN_WHDOG (Table 26) high activates the

watchdog counter. When the counter reaches zero, the

port switches to the hardware-controlled mode deter-

mined by the corresponding HWMODE_ bit. A low in

HWMODE_ switches the port into shutdown by setting

MAX5945

Quad Network Power Controller

for Power-Over-LAN

______________________________________________________________________________________ 31

ADDRESS = 1Bh

SYMBOL BIT R/W

DESCRIPTION

7 R ID_CODE[4]

6 R ID_CODE[3]

5 R ID_CODE[2]

4 R ID_CODE[1]

ID_CODE

3 R ID_CODE[0]

2 R REV [2]

1 R REV [1]

REV

0 R REV [0]

Table 23. ID Register

ID register keeps track of the device ID number and revision. The MAX5945’s ID_CODE[4:0] = 11000b. Contact the factory for

REV[2:0] value.

ADDRESS = 1Ch

SYMBOL BIT CoR

DESCRIPTION

Reserved 7 — Reserved

Reserved 6 — Reserved

Reserved 5 — Reserved

Reserved 4 — Reserved

SMODE4 3 CoR Hardware control flag for port 4

SMODE3 2 CoR Hardware control flag for port 3

SMODE2 1 CoR Hardware control flag for port 2

SMODE1 0 CoR Hardware control flag for port 1

Table 24. SMODE Register

1 2 ... 26 27 28 29 30 31 32 33 34 35 36 ... 43 44

Quad Network Power Controller 1

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