P46 TAXIING FOR DEP AT BUR ENTERED RWY WITHOUT ATC CLRNC.

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AT BUR; I RECEIVED ATIS INDICATING THE ACTIVE RWYS WERE RWY 33 AND RWY 26. I CALLED FOR MY PREFILED IFR CLRNC; AND WAS ADVISED THAT REROUTING WAS OCCURRING BY CTR AND THEY WOULD CALL BACK. WHILE WAITING; THE RUN-UP WAS COMPLETED; EXCEPT FOR LOADING THE FLT PLAN. AFTER ABOUT 10 MINS; A REQUEST FOR CLRNC INDICATED THAT HVY TFC WAS SLOWING THE PROCESS AND TO CONTACT GND; AND I WOULD GET MY CLRNC LATER. GND WAS CONTACTED AND ADVISED WE HAD THE ATIS; WERE AWAITING A CLRNC; WERE READY TO TAXI AND RUN-UP COMPLETE. I WAS ADVISED TO 'TAXI TO RWY 33; TXWY A; HOLD AT TXWY B RWY 26.' I HAD BEFORE ME THE BUR COMMERCIAL TXWY DIAGRAM. WHILE IN MOTION; I WAS ADVISED TO 'CROSS TXWY B; CROSS RWY 26; TAXI TXWY C HOLD SHORT GULF.' AT THAT MOMENT; I SAW THE SIGNAGE FOR TXWY B AND CONTINUED STRAIGHT AHEAD TO CROSS THE RWY THAT WAS NOW JUST IN FRONT OF ME. I WAS ADVISED THAT I HAD TAXIED ONTO RWY 33; AND TO EXECUTE A 180 DEG TURN; AND TAXI L ON TXWY B. I THOUGHT I HAD READ BACK WHAT I WAS DOING; BUT OBVIOUSLY; I MISUNDERSTOOD MY TAXI INSTRUCTIONS. WHEN THEY WERE CHANGED WHILE TAXIING; I WAS UNABLE TO LOOK AT THE DIAGRAM ON MY KNEE BOARD. CONTRIBUTING FACTORS TO MISUNDERSTANDING INSTRUCTIONS: 1) NOT HAVING CLRNC; SO NO CONFIRMATION WHETHER I WAS TO DEPART RWY 26 OR RWY 33. 2) HOLD SHORT INSTRUCTIONS FOR TXWYS; NOT RWYS SO A CLRNC TO CROSS A TXWY WAS NOT CLR THAT IT MEANT TO TURN ON THAT TXWY.