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22
LAN35MH08HR & LAN35ME08HR User’s Manual
WARNING: If the stack contains a +5V power supply, do not apply power via
CN23! If two +5V power supplies conflict, all boards in the stack may
be damaged or destroyed. If a stack powered by CN23 contains any
boards other than an RTD StackNET product (not recommended), be
sure the non-StackNET board(s) do not back feed +5V onto the bus
before applying power.
3.3.6
CN26
E
XTERNAL
LED,
S
WITCH
R
ESET
B
UTTON AND
T
IME
T
ICK CONNECTOR
Connector CN26 provides three different functions:
1.
External LED interface signals. Power is supplied from the even-numbered pins (LED anode). The odd-numbered pins (LED
cathode) are driven low when the LED is illuminated and tri-stated when off. Refer to Chapter 2 for the electrical specifications.
Each signal pair includes a 374 Ohm current limiting resistor. A typical LED circuit is shown below:
Figure 10: External LED Drive Circuit
2.
Pin 25 is a reset input to the VSC7428. Shorting this pin to ground with either a jumper or push button will cause the processor core
in the VSC7428 to reset, rebooting the CEServices software. Refer to the Functional Description chapter for details on the reset
behavior.
3.
Pin 23 is connected to the IEEE1588 Time Tick signal of the VSC7428. This pin can be programmed as either an input or output in
the CEServices software. It can be used as an input pulse for the synchronization of the internal 1588 master timer or as
programmable divided-frequency outputs from the internal 1588 master timer. The programmable divided frequency is between 25
MHz and 1 Hz
while the programmed output signal’s duty cycle can depend on the programmed divider factor.
Refer to Chapter 2
for the electrical specifications of this pin.
NOTE: CN26 Pin 23 is connected directly to the VSC7428. Be sure to not
exceed the voltage specifications on this pin, as the board may be
destroyed. External devices may require signal conditioning or
voltage translation to interface with the Time Tick Signal.
CN26 is a 26-pin DIL connector with 2mm pin spacing. Pin 1 is indicated by a square solder pad. The pinout is described in the table below.
Pin 25 Pin 23 Pin 21 Pin 19 Pin 17 Pin 15 Pin 13 Pin 11
Pin 9
Pin 7 Pin 5 Pin 3
Pin 1
Pin 26 Pin 24 Pin 22 Pin 20 Pin 18 Pin 16 Pin 14 Pin 12 Pin 10 Pin 8 Pin 6 Pin 4 Pin 2
Figure 11: CN26 Pin Numbering
CN26 pin functions are described as follows: