APCSnotes

26-bit Shared C library (ROM or RAM):      ARM 2 or later (26-bit)
					   Will always be in 26-bit modes
			                   Client may be APCS-32 or APCS-R

26-bit ANSILib				   ARM 2 or later (26-bit)
					   Will always be in 26-bit modes
					   Client is APCS-R

32-bit Shared C library (ROM or RAM):      ARM 6 or later (32-bit)
					   May be in 26 or 32-bit modes
				           32-bit instructions always available
					   Client is APCS-32

32-bit ANSILib				   ARM 6 or later
					   May be in 26 or 32-bit modes
				           32-bit instructions always available
					   Client is APCS-32


32-bit ANSILib will be RISC OS 3.5 or later

other requirements for any CLib or ANSILib:

RISC OS 3.1
FPEmulator 4.03 or later
CallASWI (if RISC OS 3.6 or earlier)