CPU12
HIGH-LEVEL LANGUAGE SUPPORT
MOTOROLA
REFERENCE MANUAL
C-5
The CPU12 has dedicated signal lines that allow the CPU to access the bank page
register without having to use an address in the normal 64-Kbyte address space. This
eliminates the need for the program to know where the page register is physically lo-
cated.
The RTC instruction is similar to the RTS instruction, except that RTC uses the byte
of information that was saved on the stack by the corresponding CALL instruction to
restore the bank page register to its old value. Although a CALL/RTC pair can be used
to access any function subroutine regardless of the location of the called routine (on
the current bank page or a different page), it is most efficient to access some subrou-
tines with JSR/RTS instructions when the called subroutine is on the current page or
in an area of memory that is always visible in the 64-Kbyte map regardless of the bank
page selection.
Push and pull instructions can be used to stack some or all the CPU registers during
a function call. The CPU12 can push and pull any of the CPU registers A, B, CCR, D,
X, Y, or SP.
C.9 Instruction Set Orthogonality
One very helpful aspect of the CPU12 instruction set, orthogonality, is difficult to quan-
tify in terms of direct benefit to an HLL compiler. Orthogonality refers to the regularity
of the instruction set. A completely orthogonal instruction set would allow any instruc-
tion to operate in any addressing mode, would have identical code sizes and execution
times for similar operations on different registers, and would include both signed and
unsigned versions of all mathematical instructions. Greater regularity of the instruction
makes it possible to implement compilers more efficiently, because operation is more
consistent, and fewer special cases must be handled.
Summary of Contents for CPU12
Page 8: ...MOTOROLA CPU12 viii REFERENCE MANUAL ...
Page 14: ...MOTOROLA INTRODUCTION CPU12 1 4 REFERENCE MANUAL ...
Page 20: ...MOTOROLA OVERVIEW CPU12 2 6 REFERENCE MANUAL ...
Page 38: ...MOTOROLA INSTRUCTION QUEUE CPU12 4 6 REFERENCE MANUAL ...
Page 300: ...MOTOROLA DEVELOPMENT AND DEBUG SUPPORT CPU12 8 16 REFERENCE MANUAL ...
Page 338: ...MOTOROLA MEMORY EXPANSION CPU12 10 8 REFERENCE MANUAL ...
Page 364: ...MOTOROLA INSTRUCTION REFERENCE CPU12 A 26 REFERENCE MANUAL ...
Page 386: ...MOTOROLA HIGH LEVEL LANGUAGE SUPPORT CPU12 C 6 REFERENCE MANUAL ...
Page 438: ...MOTOROLA SUMMARY OF CHANGES CPU12 S 2 REFERENCE MANUAL ...
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