Returns the size (in bytes) that a segment occupies in ROM.
SIZEOF_ROM (segmentName)
segmentName
Name of a ROM segment; must start with a period.
Always returns the value 0 until the ROM is built. Accordingly, you should use SIZEOF_ROM only within an expression inside a WRITEB, WRITEH, WRITEW, or AT function.
Furthermore, you need SIZEOF_ROM only if you use the COMPRESS option on the memory segment. Without compression, there is no difference between the return values of SIZEOF_ROM and SIZEOF.