In article <1152598467.894100.285310@m79g2000cwm.googlegroups.com>, eerobert@gmail.com wrote:> Why 8051 need 2 clock cycle for 1 system state?Dont you mean 12 to 1? And there is no magic, that is just how intel did it back then. Other implementations have different clock/instruction ratios.
8051 architecture
Started by ●July 11, 2006
Reply by ●July 13, 20062006-07-13
Reply by ●July 14, 20062006-07-14
In article <e95613$aki$1@cam-news1.cambridge.arm.com>, Joseph <joseph.yiu@somewhere-in-arm.com> writes>Peter Harrison wrote: > > >> The OP asked a question that we must assume had some meaning and >> relevance to him. Granted, it was poorly phrased and possibly ambiguous. >> However, almost nobody seems to have tried answering the question and >> most seem to have almost willfully misinterpreted it. the original >> question asks about the need for 2 clocks per machine state in the 8051. >> A quick look at the Philips databook to remind me what an 8051 was (just >> kidding - stay calm) shows that a machine cycle consists of six machine >> states, each requiring 2 clocks. So all this stuff about 1, 2, 4, 6 and >> 12 clock variants is a bit beside the point. If the OP really meant >> machine state (as written) rather than machine cycle (as read by most) >> then the question is probably quite fair. Certainly, a look at the >> Philips databook makes things a bit more clear. There is a small section >> specifically about CPU timing and Machine cycles. However, the family >> hardware guides most likely to be found by a less than thorough Google >> search don't always mention it. The 80C51 Family Architecture document >> found here: >> >> http://www.semiconductors.philips.com/acrobat_download/various/80C51_FAM_ARCH_ >1.pdf >> > >I guess the reason is the way the first generation of 8051 is designed. >(there wasn't VHDL/Verilog at that time, the chip layout was manually >created). > >At that time, registers could be implemented as latches. >So the first 8051 might have used "register" design that >required multiple clock phases to drive. For example, >1 flip-flop = 2 multiplexer latches in series >As a result, 2 clock cycles might be required to ensure correct >operation of the register. >And the design use 2 clock cycles for each machine state.At the time the 8051 was implemented they used 12 cycles. The 6, 4, 2 and 1 cycle have come about since VHDL/Verilog -- \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ \/\/\/\/\ Chris Hills Staffs England /\/\/\/\/ /\/\/ chris@phaedsys.org www.phaedsys.org \/\/\ \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
Reply by ●July 14, 20062006-07-14
Chris Hills wrote:> In article <e95613$aki$1@cam-news1.cambridge.arm.com>, Joseph > <joseph.yiu@somewhere-in-arm.com> writes > >>Peter Harrison wrote: >> >> >> >>>The OP asked a question that we must assume had some meaning and >>>relevance to him. Granted, it was poorly phrased and possibly ambiguous. >>>However, almost nobody seems to have tried answering the question and >>>most seem to have almost willfully misinterpreted it. the original >>>question asks about the need for 2 clocks per machine state in the 8051. >>>A quick look at the Philips databook to remind me what an 8051 was (just >>>kidding - stay calm) shows that a machine cycle consists of six machine >>>states, each requiring 2 clocks. So all this stuff about 1, 2, 4, 6 and >>>12 clock variants is a bit beside the point. If the OP really meant >>>machine state (as written) rather than machine cycle (as read by most) >>>then the question is probably quite fair. Certainly, a look at the >>>Philips databook makes things a bit more clear. There is a small section >>>specifically about CPU timing and Machine cycles. However, the family >>>hardware guides most likely to be found by a less than thorough Google >>>search don't always mention it. The 80C51 Family Architecture document >>>found here: >>> >>>http://www.semiconductors.philips.com/acrobat_download/various/80C51_FAM_ARCH_ >> >>1.pdf >> >>I guess the reason is the way the first generation of 8051 is designed. >>(there wasn't VHDL/Verilog at that time, the chip layout was manually >>created). >> >>At that time, registers could be implemented as latches. >>So the first 8051 might have used "register" design that >>required multiple clock phases to drive. For example, >>1 flip-flop = 2 multiplexer latches in series >>As a result, 2 clock cycles might be required to ensure correct >>operation of the register. >>And the design use 2 clock cycles for each machine state. > > > At the time the 8051 was implemented they used 12 cycles. > The 6, 4, 2 and 1 cycle have come about since VHDL/Verilog > >The 12 cycles number is machine cycle. Inside each machine cycle, it is divided into 6 states (S1-S6). Each state takes 2 clock cycles (P1 and P2). I guess this is the item that OP asked about. Joseph
Reply by ●July 15, 20062006-07-15
Chris Hills wrote:> Is it just me (and Grant Edwards) or are the questions getting worse and > pointless?It's the influence of google groups. I liken many such posts to the level once exhibited by WebTVers. Graham
Reply by ●July 17, 20062006-07-17
In article <44B8C167.EB507438@REMOVETHIS.hotmail.com>, Eeyore <rabbitsfriendsandrelations@REMOVETHIS.hotmail.com> writes:> > > Chris Hills wrote: > >> Is it just me (and Grant Edwards) or are the questions getting worse and >> pointless? > > It's the influence of google groups. >It's interesting that the most search queries on Google for both "embedded" and "google groups" (at the time of writing this) are coming from India. See: http://www.google.com/trends?q=embedded&ctab=0&geo=all&date=all http://www.google.com/trends?q=google+groups&ctab=0&geo=all&date=all However the number of queries for "google groups" compared to "embedded" are quite small: http://www.google.com/trends?q=embedded%2Cgoogle+groups&ctab=0&geo=all&date=all Simon. -- Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP If Google's motto is "don't be evil", then how did we get Google Groups 2 ?
Reply by ●July 17, 20062006-07-17
On 17 Jul 2006 08:29:16 -0500, in comp.arch.embedded clubley@remove_me.eisner.decus.org-Earth.UFP (Simon Clubley) wrote:>In article <44B8C167.EB507438@REMOVETHIS.hotmail.com>, Eeyore <rabbitsfriendsandrelations@REMOVETHIS.hotmail.com> writes: >> >> >> Chris Hills wrote: >> >>> Is it just me (and Grant Edwards) or are the questions getting worse and >>> pointless? >> >> It's the influence of google groups. >> > >It's interesting that the most search queries on Google for both "embedded" >and "google groups" (at the time of writing this) are coming from India. > >See: > >http://www.google.com/trends?q=embedded&ctab=0&geo=all&date=all >http://www.google.com/trends?q=google+groups&ctab=0&geo=all&date=all > >However the number of queries for "google groups" compared to "embedded" >are quite small: > >http://www.google.com/trends?q=embedded%2Cgoogle+groups&ctab=0&geo=all&date=all > >Simon. >If Google's motto is "don't be evil", then how did we get Google Groups 2 ?They should have started with "Do No Harm" motto martin