[Motorola] COR output on SM50 Radio

[Eric Lemmon]

Bob,

Pin 8 on the SM50 accessory connector is an open-collector output that
can be programmed in the RSS for any one of four functions:  Null, CSQ
Detect, PL/DPL & CSQ Det, or External Alarm.  The output can sink up to
200 mA, and its saturation (low) level is about 0.3 VDC.  The SM50 radio
does not have a pull-up resistor on the Pin 8 output, so that must be
provided externally.

The terms High and Low for Active Level options in the SM50 RSS can be
misleading.  Active Low means that the pin is normally floating, and is
pulled to ground when the function is true.  Active High means that the
pin is normally pulled to ground, and is allowed to float when the
function is true.  Active High logic requires an external pull-up
resistor to work properly, unless the pull-up is an inherent feature of
the external controller.  Be careful to keep the sinking current well
below 200 mA.

When using the Pin 8 output for COR control, the signal common (ground)
at Pin 7 should be connected between the SM50 and the external
controller.  Failure to include the signal common connection may have
bizarre consequences!

73, Eric Lemmon WB6FLY

--- "Bob" <gopher7 at 9... wrote---

I am having trouble with the COR line (Pin 8) on a Motorola SM50 I am
using for a link radio on a repeater I am building.  Specs I have say
pin 8 is COR, active low and "programmable." what are my choices for
programming this line, and how is it accomplished?

I have installed a pull-up resistor on the line (2200 ohm) but when I
receive a valid signal (with required PL) the radio "pulses" in and out
of RX mode very fast which leads me to believe the COR line cannot sink
the current on that line. I have tried increasing the value of the
resistor to 100 K ohms with no change.

Has anyone else had these issues, and what did you do for a work around?