MC81F4x16
This flag is set to match the sign bit (bit 7) status of the result of a data or arithmetic operation. When
the BIT instruction is executed, bit 7 of memory is copied to this flag.
9.2 Program Memory
A 16-bit program counter is capable of addressing up
to 64K bytes, but this device has 32K bytes program
memory space only physically implemented. Accessing
8000H
a location above FFFFH will cause a wrap-around to
0000H.
9000H
Figure 9-6 shows a map of Program Memory. After
reset, the CPU begins execution from reset vector
which is stored in address FFFEH and FFFFH. As
shown in Figure 9-6, each area is assigned a fixed
location in Program Memory.
0A000H
Program memory area contains the user program Page
Call (PCALL) area contains subroutine program to
0E000H
0F000H
reduce program byte length by using 2 bytes PCALL
instead of 3 bytes CALL instruction. If it is frequently
called, it is more useful to save program byte length.
Table Call (TCALL) causes the CPU to jump to each
TCALL address, where it commences the execution of
the service routine. The Table Call service area spaces
2-byte for every TCALL: 0FFC0H for TCALL15,
0FEFFH
0FF00H
0FFC2H for TCALL14, etc., as shown in Figure 9-7.
0FFC0H
The interrupt causes the CPU to jump to specific
location where it commences the execution of the
service routine. The interrupt service locations spaces
2-byte interval. The External interrupt 1, for Example, is
assigned to location 0FFFCH.
TCALL Area
0FFDFH
0FFE0H
Interrupt
Vector Area
0FFFFH
Any area from 0FF00H to 0FFFFH, if it is not going to
be used, its service location is available as general
purpose Program Memory.
Figure 9-6 Program Memory Map
52
October 19, 2009 Ver.1.35
FINECHIPS [ FINECHIPS ]
