Nicron #12 20 декабря 1996

Ассемблер     Программирование

Programming - a course of study assembler Wlodek Black, continued.

                                                         Z80

(Continued).

(C) WLODEK BLACK

      00Bh. GROUP commands for the individual bits.

The group includes two types of commands for changing the 
status of individual bits, and one subgroup of commands for the 
analysis status bits.

SET - set the bit to 1;
RES - reset the bit to 0;
BIT - find out the status bits.
Addressing modes - A, B, C, D, E, H, L, (HL), (IX + nn), (IY + 
nn). Full record team is made up of mnemonics, numbers of bits 
and addresses of operands: SET 0, E

RES 7, (HL)
BIT 1, (IX +1).

SET command sets the appropriate bit to 1, the team RES -
resets to 0. The SET and RES do not affect the flagi.Primenenie
installation commands and reset bit is practiced in the 
programming of external devices that are included as memory 
cells, a procedure to correct the data, such as transcoding 
lowercase capitalization, in the algorithms of calculations and 
so on. 

BIT Team enters inversion specified in the command bit in the 
sign of zero-Z, after which he can be monitored by conditional 
jump commands. Why is stored inversion bit, but not direct 
value? Recall that set the zero flag Z = 1 indicates that the 
true condition of p and e n a t c a zero. If the bit is 0, then 
the flag will be put to 1, ie to create the conditions of 
vanishing. Invert bit is introduced for programming convenience.

When we write "JR Z ,..." after "BIT ...", we mean the 
vanishing of the scanned bit. Of course, it's convenient. BIT 
Team also supports all of these addressing modes. In addition 
to the flag Z, BIT command affects the flags of P / V and S, 
but it impact is uncertain and can not be used.


BIT 2, L
BIT 0, (HL)
BIT 7, (IX +0).

[End of 7 th Text].