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= &38 8VHU¶V 0DQXDO 0DQXDO 2EMHFWLYHV This user manual describes the architecture and instruction set of the Z80 CPU. $ERXW 7KLV 0DQXDO ZiLOG recommends that the user read and understand everything in this manual before setting up and using the product. However, we recognize that users have different styles of learning: some will want to set up and use their new evaluation kit while they read about it;...
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= &38 ,QVWUXFWLRQ 'HVFULSWLRQ Presents the User’s Manual instruction types, addressing modes and instruction Op Codes. = ,QVWUXFWLRQ 6HW Presents an overview of the User’s Manual assenbly language, status indicator flags and the Z80 instructions. 5HODWHG 'RFXPHQWV Part Number Title DC number...
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= &38 8VHU¶V 0DQXDO [YLL 8VH RI WKH 7HUPV /6% DQG 06% In this document, the terms LSB and MSB, when appearing in upper case, mean least significant byte and most significant byte, respectively. The lowercase forms, msb and lsb, mean least significant bit and most significant bit, respectively.
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8VHU¶V 0DQXDO = &38 [YLLL 5HJLVWHU $FFHVV $EEUHYLDWLRQV Register access is designated by the following abbreviations: Designation Description Read Only Read/Write Write Only – Unspecified or indeterminate 7UDGHPDUNV Z80, Z180, Z380 and Z80382 are trademarks of ZiLOG, Inc. 80 0DQXDO 2EMHFWLYHV...
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8-bit registers or as 16-bit register pairs. In addition, there are two sets of accumulator and flag registers. The Z80 CPU also contains a Stack Pointer, Program Counter, two index registers, a register, and an register.
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= &38 %ORFN 'LDJUDP &38 5HJLVWHUV The Z80 CPU contains 208 bits of R/W memory that are available to the programmer. Figure 2 illustrates how this memory is configured to eighteen 8-bit registers and four 16-bit registers. All Z80 registers are implemented using static RAM.
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< %27 7UGT U /CPWCN HhvÃSrtvr ÃTr 6yr hrÃSrtvr ÃTr 6ppyh Ayht 6ppyh Ayht Aà 6à 7à 7à Brr hy Q r 9à @à Srtvr Cà Gà Dr ÃWrp Hr ÃSrs ru DqrÃSrtvr à Trpvhy Q r DqrÃSrtvr Srtvr ThpxÃQvr Q t hÃ8r )LJXUH = &38 5HJLVWHU &RQILJXUDWLRQ 6SHFLDO3XUSRVH 5HJLVWHUV 3URJUDP &RXQWHU 3& The program counter holds the 16-bit address of the current instruction being fetched from memory.
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,QWHUUXSW 3DJH $GGUHVV 5HJLVWHU , The Z80 CPU can be operated in a mode where an indirect call to any memory location can be achieved in response to an interrupt. The...
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< %27 7UGT U /CPWCN $FFXPXODWRU DQG )ODJ 5HJLVWHUV The CPU includes two independent 8-bit accumulators and associated 8- bit flag registers. The accumulator holds the results of 8-bit arithmetic or logical operations while the register indicates specific conditions FLAG for 8-bit or 1 16-bit operations, such as indicating whether or not the result of an operation is equal to zero.
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ALU, and provide required external control signals. 3,1 '(6&5,37,21 2YHUYLHZ The Z80 CPU I/O pins are illustrated in Figure 3 and the function of each is described in the following paragraphs. 80 2YHUYLHZ...
< %27 7UGT U /CPWCN MREQ IORQ System Control RFSH Address HALT WAIT Z80 CPU Control RESET BUSRQ BUSACK Control Data )LJXUH = ,2 3LQ &RQILJXUDWLRQ 3LQ )XQFWLRQV $±$ Address Bus (output, active High, tristate). A15-A0 form a 16-bit address bus.
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< %27 7UGT U /CPWCN %86$&. Bus Acknowledge (output, active Low). Bus Acknowledge indicates to the requesting device that the CPU address bus, data bus, and control signals MREQ, IORQ RD, and WR have entered their high-impedance states. The external circuitry can now control these lines. %865(4 Bus Request (input, active Low).
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< %27 7UGT U /CPWCN ,254 Input/Output Request (output, active Low, tristate). IORQ indicates that the lower half of the address bus holds a valid I/O address for an I/O read or write operation. IORQ is also generated concurrently with M1 during an interrupt acknowledge cycle to indicate that an interrupt response vector can be placed on the data bus.
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< %27 7UGT U /CPWCN the interrupt status to Mode 0. During reset time, the address and data bus go to a high-impedance state, and all control output signals go to the inactive state. Notice that RESET must be active for a minimum of three full clock cycles before the reset operation is complete.
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< %27 7UGT U /CPWCN 7,0,1* 2YHUYLHZ 7KH = &38 H[HFXWHV LQVWUXFWLRQV E\ VWHSSLQJ WKURXJK D SUHFLVH VHW RI EDVLF RSHUDWLRQV 7KHVH LQFOXGH • Memory Read or Write • I/O Device Read or Write • Interrupt Acknowledge $OO LQVWUXFWLRQV DUH VHULHV RI EDVLF RSHUDWLRQV (DFK RI WKHVH RSHUDWLRQV FDQ WDNH IURP WKUHH WR VL[ FORFN SHULRGV WR FRPSOHWH RU WKH\ FDQ EH OHQJWKHQHG WR V\QFKURQL]H WKH &38 WR WKH VSHHG RI H[WHUQDO GHYLFHV 7KH FORFN SHULRGV DUH UHIHUUHG WR DV 7 WLPH F\FOHV DQG WKH RSHUDWLRQV DUH...
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< %27 7UGT U /CPWCN 7DEOH %XEEOH /LVWLQJ &RQWLQXHG 2EM &RGH 6WPW 6RXUFH 6WDWHPHQW length of data array first element in comparison second element in comparison flag to indicate exchange unused pointer into data array unused 0000 222600 sort: ld (data), hl ;...
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< %27 7UGT U /CPWCN Top of stack (SP) (SP+1) • • • • LQVWUXFWLRQ LV WKH H[DFW UHYHUVH RI D $OO PUSH PUSH LQVWUXFWLRQV XWLOL]H D ELW RSHUDQG DQG WKH KLJK RUGHU E\WH LV DOZD\V SXVKHG ILUVW DQG SRSSHG ODVW PUSH BC is PUSH 8 then C PUSH DE...
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< %27 7UGT U /CPWCN -XPS *URXS -3 QQ 1RGTCVKQP 3& QQ 1R %QFG 1RGTCPFU Note: The first operand in this assembled object code is the low order byte of a two-byte address. &GUETKRVKQP 2SHUDQG LV ORDGHG WR UHJLVWHU SDLU 3& 3URJUDP &RXQWHU 7KH QH[W LQVWUXFWLRQ LV IHWFKHG IURP WKH ORFDWLRQ GHVLJQDWHG E\ WKH QHZ FRQWHQWV RI WKH 3& 0 &\FOHV...
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< %27 7UGT U /CPWCN 5(7, 1RGTCVKQP 5HWXUQ IURP ,QWHUUXSW 1R %QFG 5(7, &GUETKRVKQP 7KLV LQVWUXFWLRQ LV XVHG DW WKH HQG RI D PDVNDEOH LQWHUUXSW VHUYLFH URXWLQH WR • Restore the contents of the Program Counter (PC) (analogous to the RET instruction) •...
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< %27 7UGT U /CPWCN B generates an interrupt and is acknowledged. The interrupt enable out, IEO, of B goes Low, blocking any lower priority devices from interrupting while B is being serviced. Then A gen- erates an interrupt, suspending service of B. The IEO of A goes Low, indicating that a higher priority device is being serviced.
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