Toshiba TMP87CP24AF - Manual (Page 14)

TOSHIBA
TMP87CM24A/P24A
Example: BCD operation
(The A becomes 4?H after executing the following program when A = 19 h , B = 28 h )
ADD A, B ; A<-41 h , HF<-1,CF<-0
DAA A ; A 41H + 06 h = 4?H (decimal-adjust)
(4) Jump status flag (JF)
Zero or carry information is set to the JF after operation (e. g. INC, ADD, CMP, TEST).
The JF provides the jump condition for conditional jump instructions [JRS T/F, $-F2-hd], [JR T/F,
$ -F 2 -hd] (T or F is a condition code). Jump is performed if the JF is "1" for a true condition (T), or the
JF is "0" for a false condition (F).
The JF is set to "1" after executing the load/exchange/swap/nibble rotate/jump instruction, so that
[JRS T, $ -F 2 -F d] and [JR T, $ - f 2 - f d] can be regarded as an unconditional jump instruction.
Example : Jump status flag and conditional jump instruction
; Jump when a carry is caused by the immediately
preceding operation instruction.
; JF is set to "1" by the immediately preceding
instruction, making it an unconditional jump
instruction.
INC A
JRS T, SLABLE1
LD A,(HL)
JRS T, SLABLE2
Example : The accumulator and flags become as shown below after executing the following instructions
when the WA register pair, the HL register pair, the data memory at address OOCS h , the carry flag
and the half carry flag contents being "219A h ", "OOCS h ", "D7 h ", "1" and "0", respectively.
Instruction
Acc. after
execution
Flag after execution
JF ZF CF HF
ADDC A, (HL) 72 1 0 1 1
SUBB A, (HL) C2 1 0 1 0
CMP A, (HL) 9A 0 0 1 0
AND A, (HL) 92 0 0 1 0
LD A, (HL) D7 1 0 1 0
ADD A, 66H 00 1 1 1 1
Instruction
Acc. after
execution
Flag after execution
JF ZF CF HF
INC A 9B 0 0 1 0
ROLC A 35 1 0 1 0
RORC A CD 0 0 0 0
ADD WA,0F508H 16A2 1 0 1 0
MUL W, A 13DA 0 0 1 0
SET A.5 BA 1 1 1 0
1.7 Stack and Stack Pointer
1.7.1 Stack
The stack provides the area in which the return address or status, etc. are saved before a jump is
performed to the processing routine during the execution of a subroutine call instruction or the
acceptance of an interrupt. On a subroutine call instruction [CALL a]/[CALLP n]/[CALLV n], the contents of
the PC (the return address) is saved; on an interrupt acceptance, the contents of the PC and the PSW are
saved (the PSW is pushed first, followed by PC h and PC l ). Therefore, a subroutine call occupies two bytes
on the stack; an interrupt occupies three bytes.
When returning from the processing routine, executing a subroutine return instruction [RET] restores the
contents to the PC from the stack; executing an interrupt return instruction [RETI]/[RETN] restores the
contents to the PC and the PSW (the PC l is popped first, followed by PC h and PSW).
The stack can be located anywhere within the data memory space except the register bank area,
therefore the stack depth is limited only by the free data memory size.
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24-14 2002
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10-03