6502 instruction cycle timings
How does the 6502 work?
The 6502 at the heart of the Beeb is simple but powerful. Like most other processors, instructions are fetched from RAM and executed in turn. The 6502 has a very simple pipeline — the fetch for the next instruction happens during the execution of the previous instruction. This has important consequences that we’ll talk about later.
Why is the 65CE02 faster than the 65xx?
The 65CE02 can recover faster from engagement of the SYNC signal, which reduces the minimum instruction execution time from 2 cycles to 1 cycle. These improvements allow the 65CE02 to execute code up to 25% faster than previous 65xx models.
Why is the 65CE02 redesigned?
Internally, the pipeline of the 65CE02 was redesigned to reduce the number of cycles required to execute an instruction. The 65CE02 can recover faster from engagement of the SYNC signal, which reduces the minimum instruction execution time from 2 cycles to 1 cycle.
How many cycles did the 6502 execute?
As far as the 6502 is concerned it only executed 6 cycles, but because its external clock was slowed down, the wall-clock time taken is 10 2MHz ticks. This example shows three stretches.
Jsbeeb Part Three - 6502 CPU Timings
This is the third post in my series on emulating a BBC Micro in Javascript. Youmight find it instructive to read the first part which covers generalstuff, or the second partwhich focuses on the video hardware. This postwill cover the subtleties of the 6502’s instruction timings. In the next postI’ll cover how interrupts and hardware timers fit into
Why Is Timing So Important Anyway?
Getting the instruction timings right is paramount for good emulation. Icovered some of this in the first post, but so many tricks on the BBCrequired intimate knowledge of the instruction and hardware timings that if anemulator didn’t account for them properly, some things wouldn’t work right. The most challenging example of timings were games prot
Life of An Instruction
The 6502 at the heart of the Beeb is simple but powerful. Like most otherprocessors, instructions are fetched from RAM and executed in turn. The 6502has a very simple pipeline — the fetch for the next instruction happens during the execution of the previous instruction. This has importantconsequences that we’ll talk about later. Most CPUs have a ph
Wait Around For Ages and Then Two Turn Up at Once
Just when you thought all this was making sense, there’s another thing toconsider. Inside the Beeb there are two buses. Fast peripherals and RAMcan run at the same speed as the CPU itself and are clocked at 2MHz. Some ofthe peripherals can’t work at this blazing speed, and instead need to becommunicated with at the slothly 1MHz. These peripherals a
Implementation Details
jsbeebimplements all the complex behaviour by “compiling” instructions from atable of opcode side effects and knowledge of what addressing modes cause whatkinds of memory accesses. A list of cycles where memory accesses is kept, andthen an optimization pass is made: any memory accesses that are known not torefer to any hardware devices (and thus do
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6502.pdf
(can be used for single instruction execution}. ?RDY Signal. (can be used for single cycle execution). • Two Phase Output Clock for Timing of Support Chips. |
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W65C02S 8–bit Microprocessor
08.04.2022 Read-Modify-Write add 2 cycles. 4. New addressing mode for W65C02S. 5. The BRK instruction for both the NMOS 6502 and 65C02 is a 2 byte ... |
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Appendix 1: 6502 Instruction Set
Number of machine cycles needed to complete instruction There is one more 6502 addressing mode which we have not covered in the ... timing 182-5. |
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W65C02S 8–bit Microprocessor
08.10.2018 The Timing Control Unit (TCU) provides timing for each instruction cycle that is executed. The TCU is set to zero for each instruction fetch ... |
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Diploma thesis
16.07.2012 Additionally the timing of the gate voltage function depends on the ... Instructions on the 6502 generally need as many cycles to execute as ... |
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Rockwell
R6502 software and timing compatible. • 10 new instructions for faster and smaller instructions require three instruction cycles and the pull instruc. |
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OpenCores 6502 IP Core Specification
15.09.2018 Figure (4): ADC SBC – Timing Diagram “Zero Page” . ... Now talking about the specification of the 6502 True Cycle Core IP. |
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The Design and Implementation of the Nintendo Entertainment System
09.12.2004 Appendix C: 6502 Instruction Clock Cycles. ... The timing control module generates the cycle number that the processor is currently ... |
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The Ultimate C64 Overview
the 6502 was to have a reduced instruction set and a small register file making it simpler and cycle-exact timing of assembly code to switch a VIC. |
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Altirra Hardware Reference Manual - VirtualDub
07.07.2022 Cycle timing . ... Table 37: Disk drive transmit timings by ... CPU: Fixed some erroneous illegal instructions in the 6502 opcode chart. |
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6502 - Description
(can be used for single instruction execution) • RDY Signal (can be used for single cycle execution) Two Phase Output Clock for Timing of Support Chips AB3 |
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6502pdf - Description
Pin compatible with NMOS R6502 The timing control unit keeps track of the instruction cycle being The unit is set to zero each time an instruction fetch is |
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Rockwell datasheet - 6502org
Software compatible with R6502 enhancements over their NMOS counterpart, the R6502 The timing control unit keeps track of the instruction cycle being |
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65CE02 MICROPROCESSOR - 6502org
10MHz (100ns instruction cycles) and the 65CE02 is capable of a 350 decrease in program execution time compared to a standard 4MHz 6502 The 65CE02 |
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W65C02
8 oct 2018 · WDC reserves the right to make changes at any time without notice The Timing Control Unit (TCU) provides timing for each instruction cycle The BRK instruction for both the NMOS 6502 and 65C02 is a 2 byte instruction |
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Appendix 1: 6502 Instruction Set
Number of machine cycles needed to complete instruction A variable bit in ly, using some time-sharing principle which need not concern us here If the end of |
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W65C02S Microprocessor DATA SHEET - Index of
WDC reserves the right to make changes at any time without notice in order to The Timing Control Unit (TCU) provides timing for each instruction cycle that is The BRK instruction for both the NMOS 6502 and 65C02 is a 2 byte instruction |
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6502 - Computer Science, Columbia University
Timing Generator Operation of the processor is further complicated by the fact that all instructions take multiple clock cycles depending on the addressing mode |
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NESPACS 6502
The 6502 was revolutionary at its time and is cited as one of only one register can write to a bus on any given cycle Figure 1 3: Single byte instruction timing |
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Mos_65ce02_mpupdf
10MHz (100ns instruction cycles) and the 65CE02 is capable of a 350 decrease in program execution time compared to a standard 4MHz 6502 The 65CE02 |
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