Z80 conditional jump

Z80 Instructions Conditional Jump Group DJNZ e Description: • The B register is decremented, and if a non zero value remains, the value of the displacement e is added to the PC. • The next instruction is fetched from the location designated by the new contents of the PC. • The jump has a range of -126 to +129 bytes. Z80 Instruction Set Summary Written by Jonathan Bowen ... Conditional Jump Unconditional Jump Conditional Jump Load Load Load and Decrement Load, Dec., Repeat
The Z80 also contains flags to control the flow of a program. The flags are changed whenever an arithmetic operation is done and the flags can be tested one at a time by a jump instructions to change the flow of the program, depending on the state of the flag. The flags record the sign (S), zero (Z), half-carry (H),... The Z80 in the ZX spectrum, Sam Coupe and the CPC are wired oddly... they use 16 bit ports and use BC as the port number - even though the assembly command is Out (C) the command in the assembly code is not the one that effectively occurs when the Z80 runs it.... The Z80 is one of the most popular microprocessors of the 80's having been used in many home computers systems of that era. This document will give an introduction to all aspects of the Z80 assuming no knowledge of programming.

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Sep 18, 2017 · All these changes should make the API better organized and easier to use. 1.0.2 (12th February 2014) Conditional relative jump (JR_DD_E) instructions such as "jr NZ, loop_label" were not decoded correctly, just a silly bug in a macro to extract bits. An indirect branch (also known as a computed jump, indirect jump and register-indirect jump) is a type of program control instruction present in some machine language instruction sets. Rather than specifying the address of the next instruction to execute , as in a direct branch , the argument specifies where the address is located.
The following has been adapted from an abbreviated summary of the Z80 instruction set, ... Conditional Jump: If Carry = 1: ... then the highest is when the jump is ... You'll hate this answer - it depends on the architecture. Typically conditional jumps (or branches) depend on a previous instruction performing some kind of comparison, subtraction, or addition instruction setting processor flags that indicate on... Apr 17, 2017 · lecture 18 jump, unconditional jump, conditional jump and compare cmp, jmp in assembly in urdu hindi ... ٢-شرح برمجة MP Z80 الفرق بين ADD و ADC - Duration: 5:30. Yousef Magid ...

JR JR imm8 The signed 8 bit value imm8 is added to PC, allowing a jump within 128 bytes of the instruction. May also be conditional, but only with Z, NZ, C, and NC arguments. CALL CALL imm16 The current value of PC+3 is PUSHed, then imm16 is loaded into PC. May be conditional with the same syntax and arguments as JP, although (HL) is not valid. A jump is unconditional and the bits saved by leaving out the condition can be used for the address. A jump allows for a 26 bit address and so can jump much further in the code than a branch. At the expense of not being conditional.
An indirect branch (also known as a computed jump, indirect jump and register-indirect jump) is a type of program control instruction present in some machine language instruction sets. Rather than specifying the address of the next instruction to execute , as in a direct branch , the argument specifies where the address is located. JR JR imm8 The signed 8 bit value imm8 is added to PC, allowing a jump within 128 bytes of the instruction. May also be conditional, but only with Z, NZ, C, and NC arguments. CALL CALL imm16 The current value of PC+3 is PUSHed, then imm16 is loaded into PC. May be conditional with the same syntax and arguments as JP, although (HL) is not valid.

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HL | |EX [SP],xx|-----|Exchange |[SP]->xx | |EX AF,AF' |-----|Exchange |AF->AF' | |EX DE,HL ...
JR JR imm8 The signed 8 bit value imm8 is added to PC, allowing a jump within 128 bytes of the instruction. May also be conditional, but only with Z, NZ, C, and NC arguments. CALL CALL imm16 The current value of PC+3 is PUSHed, then imm16 is loaded into PC. May be conditional with the same syntax and arguments as JP, although (HL) is not valid. Z80, the 8-bit Number Cruncher Author: Andre Adrian Version: 04.Jun.2011 The Z80 was a 8-bit CPU presented by Zilog in 1976. It was like the Intel 8085 (1976) an improved Intel 8080 design.