Problem with update inside a procedure

I have wrote a simple procedure to update 2 fields in a table. The problem is only one field (MEASUREMENT) get updated but the other field (TIME_STAMP) is ignored. It works when I manually run the same update statement in SQL/PLUS. Any help is appreciated.

-Leo

CREATE OR REPLACE procedure CREATE_TELEMETRY (ptvID IN NUMBER,

                                value IN NUMBER, time_stamp IN NUMBER)

• update TELEMETRY_LATEST IF c > 0 THEN UPDATE TELEMETRY_LATEST set TIME_STAMP = time_stamp, MEASUREMENT = value WHERE PTV_ID=ptvID ; ELSE INSERT INTO TELEMETRY_LATEST (PTV_ID, TIME_STAMP, MEASUREMENT) VALUES (ptvID, time_stamp, value); END IF;