MT.EXTOP - call supervisor mode routine. On input, D0.B is 3 and A2 contains the address of a routine to call in supervisor mode. On entry to the specified routine, all the caller's register values will have been preserved, exceopt that a copy of the system varibles base address will have been put into D0.L. The specified routine must exit with an RTE instruction. On return from the trap call, all registers are exactly the way the specified routine left them when it issued its RTE. --------- Use of this trap instead of "TRAP #0" is is a major enhancement. MT.EXTOP uses the value 3 for D0.B, which was previously reported as an invalid manager trap. This trap call avoids a great number of problems that the internal code had with callers that just might try to enter code when they were already in supervisor mode. Functionally, MT.EXTOP will call a routine (specified in A2.L) in supervisor mode, putting the system variables base address in D0.L and requiring that code to issue an RTE when it is done. Prior to entry to that code, D0.L is given a copy of the sytem variables base address, which can prove rather handy. It is entirely up to the called code what registers it returns. The advantages of this technique over the use of "TRAP #0" are huge. There is now just one "TRAP #0" call in the ROM, which is only the one for a software reset, used by TK2's RES_128 (and by Basic by "CALL 390,").