Fujitsu F2MC-16LX Hardware Manual page 53

❍ Overflow flag (V)
This flag is set when an overflow occurs to indicate a signed numeric value as a result of an
arithmetic operation. It is cleared if no overflow occurs.
❍ Carry flag (C)
This flag is set when a carry-up or carry-down is generated from the MSB as a result of an
arithmetic operation. It is cleared if no carry-up or carry-down occurs.
■ Register Bank Pointer (RP)
The register bank pointer (RP) indicates the relationship between the general-purpose register
2
of the F
the register bank which is currently used by the conversion expression [000180
The RP consists of five bits and can have a value from 00
bank in the memory area 000180
However, when the memory in this range is not internal RAM, the register cannot be used as a
general-purpose register. The contents of RP are all initialized to "0" by a reset. From the
viewpoint of an instruction, it is possible to transfer an 8-bit immediate value to the RP, but only
the lower five bits of the data are actually used.
■ Interrupt Level Mask Register (ILM)
The interrupt level mask register (ILM) consists of three bits that indicate the level of the CPU
interrupt mask. Only interrupt requests whose levels are higher than the level indicated by
these three bits are accepted. As shown in Table 2.4-1, level 0 is defined as the highest and
level 7 is defined as the lowest. In order that an interrupt is accepted, a value which is smaller
than the value retained by the current ILM must be requested. When the interrupt is accepted,
its level value is stored in the ILM, and any subsequent interrupt with equal or lower priority is
not accepted. The contents of ILM are all initialized to "0" by a reset. From the viewpoint of the
instruction, it is possible to transfer an 8-bit immediate value to the ILM, but only the lower three
bits of the data are actually used.
Figure 2.4-11 Structure of the Interrupt Level Register (ILM)
MC-16LX and its internal RAM address. The RP indicates the first memory address of
H
Figure 2.4-10 Structure of the Register Bank Pointer (RP)
12
bit
B4
Initial value
0
15
bit
ILM2
Initial value
H
to 00037F .
H
11 10 9
8
B3 B2 B1 B0 : RP
0 0 0 0
14 13
ILM1 ILM 0 : ILM
0 0 0
2.4 Dedicated Registers
+ (RP)*10
H
to 1F . It can also assign a register
H
].
H
37