SMW Memory Map
|$7E0DC0||1 byte||Counter||Green star block coin counter. Starts at 30 (#$1E) at the beginning of a level, and decrements for each coin that is collected. Adjusts content of green star block when it hits zero. (A 1-Up mushroom comes out, instead of a spinning coin.)
It is also used in Chocolate Island 2 to count how many coins have been collected since the start of the level, and determine what sublevel data should be loaded.