Date   : Fri, 07 Apr 1989 16:22:49 MEZ
From   : I2040401%DBSTU1.BITNET@CUNYVM.CUNY.EDU
Subject: New Processor Rumours

The new Zilog Z280 processor is not a rumour! It is available in
Germany for 59.61 DM (some 32 US$, without VAT, single unit
price). The lastest revision is "J". It has no longer the cache
problem that was known with revision "G".

Some features have been mentioned on the net but there are still
more highlights:
   - It is fully software compatible with the Z80.
   - It uses less memory cycles than the Z80, e.g.
     EX DE,HL   EXX    LD A,B   all use only 2 cycles
   - It has new addressing modes:
     It has 16 bit displacements, e.g. LD A,(IX+1234H)
     It has a PC-relative addressing mode.
     It has a SP-relative addressing mode, e.g. LD (SP+1234H),5
     It has a so called "base index" addressing mode, e.g.
        LD (HL+IX),6   LD (HL+IY),7  LD (IX+IY),8
     You can also use 16 bit displacements with HL:  LD A,(HL+5678H)
   - Some other highlights:
     You can use the lower and upper half of the IX and IY registers
     individually (just as with HL). They are called IXL,
     IXH, IYL and IYH, e.g. "LD A,IXH". (These were unofficial
     instructions with the Z80.)

     It has 16 bit arithmetic, e.g.
        ADDW HL,1234H        16 bit add
        CPW  HL,BC           16 bit compare
        DECW (1234H)         16 bit decrement
        DIVW DEHL,1234H      16 bit divide
        DIVUW DEHL,BC        16 bit unsigned divide
        also signed and unsigned 16 bit multiply
        (there are also multiply and divide for 8 bits)
        NEG HL               16 bit twos complement
        SUBW HL,DE           no longer OR A   SBC HL,DE

     You can do
        CALL (HL)
        CALL cc,(HL)        conditional call
        INW HL,(C)          16 bit I/O
        PUSH 1234H
        LD (1234H),5678H
      and several other instructions, e.g. to handle the on-chip
      peripherals.

As far as I know the Z280 is the same chip as the one announced as
Z800 some years ago. It is not the same as the Z180 (= Hitachi 64180)
which has only a few new instructions.

                                          Ulf Gruene
                             Technische Universitaet Braunschweig
                                         West Germany
                                    I2040401@DBSTU1.BITNET


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