rudolpe@prism.cs.orst.edu (Eric Rudolph) (04/03/91)
I need to know about how VPA* VMA* E* and AS* are related. I have one timing diagram for them and a little chart that tells the relative timings, but I need to know WHAT they do and how they relate in English. Things like "what would happen if the device didn't assert VPA" and "Why does the 68k assert VMA* and how does it relate to VPA*" stuff like that.... I would be very grateful. I am designinga the famed speedup circuit for the Amiga.... Thanks rudolpe@jacobs.cs.orst.edu rudolpe@mist.cs.orst.edu rudolpe@ure.cs.orst.edu and if you could spare the call 503-745-7466 (oregon) after 5.
rainer@boulder.Colorado.EDU (Rainer Malzbender) (04/03/91)
In article <1991Apr02.174845.5076@lynx.CS.ORST.EDU> rudolpe@prism.CS.ORST.EDU (Eric Rudolph) writes: > >I need to know about how VPA* VMA* E* and AS* are related. I have one >timing diagram for them and a little chart that tells the relative >timings, but I need to know WHAT they do and how they relate in English. >Things like "what would happen if the device didn't assert VPA" and >"Why does the 68k assert VMA* and how does it relate to VPA*" stuff like >that.... I would be very grateful. I am designinga the famed speedup circuit >for the Amiga.... VPA, VMA, and E are used to interface to older 6800-style peripheral chips. E is a clock that is the CPU clock divided by 10. VPA and VMA mean "valid peripheral address" and "valid memory address" (I think - all my hardware manuals are at home). They basically inform the 68000 that it is talking to a 6800 peripheral. I could dig up the databook later, but I'm almost positive you don't have to worry about these signals at all if you're designing for the Amiga. On my 68000 designs I never use VPA and VMA; sometimes I use E if I need a slower clock. BTW, is the "famed speedup circuit" a 68030 or something ? -- Rainer Malzbender Save a dinosaur - buy DEC. Dept. of Physics (303)492-6829 U. of Colorado, Boulder rainer@boulder.colorado.edu 128.138.240.246
mcmahan@netcom.COM (Dave Mc Mahan) (04/04/91)
In a previous article, rainer@boulder.Colorado.EDU (Rainer Malzbender) writes: >In article <1991Apr02.174845.5076@lynx.CS.ORST.EDU> rudolpe@prism.CS.ORST.EDU (Eric Rudolph) writes: >> >>I need to know about how VPA* VMA* E* and AS* are related. I have one >>timing diagram for them and a little chart that tells the relative >>timings, but I need to know WHAT they do and how they relate in English. >>Things like "what would happen if the device didn't assert VPA" and >>"Why does the 68k assert VMA* and how does it relate to VPA*" stuff like >>that.... I would be very grateful. I am designinga the famed speedup circuit >>for the Amiga.... > >VPA, VMA, and E are used to interface to older 6800-style peripheral chips. >E is a clock that is the CPU clock divided by 10. VPA and VMA mean "valid >peripheral address" and "valid memory address" (I think - all my hardware >manuals are at home). They basically inform the 68000 that it is talking >to a 6800 peripheral. I could dig up the databook later, but I'm almost >positive you don't have to worry about these signals at all if you're >designing for the Amiga. On my 68000 designs I never use VPA and VMA; >sometimes I use E if I need a slower clock. Be careful here!! I know for a fact that the CIA chips on the amiga use the E-clock to provide proper clocking for things like the disk drive. You MUST preserve the frequency and the relative phase of the clock with respect to other signals, or your floppy disks won't work and your time-of-day clock will run fast/slow. Other strange things happen if you mess with the E-clock on an amiga. I'd post an article in comp.sys.amiga.tech and find out the answers if you don't want to get burned. Try and get a response from Dave Haynie if you can. He designed it. >Rainer Malzbender Save a dinosaur - buy DEC. >Dept. of Physics (303)492-6829 >U. of Colorado, Boulder rainer@boulder.colorado.edu 128.138.240.246 -dave -- Dave McMahan mcmahan@netcom.com {apple,amdahl,claris}!netcom!mcmahan
cs1598@athena.ecs.csus.edu (04/04/91)
In article <1991Apr3.215104.21550@netcom.COM> mcmahan@netcom.COM (Dave Mc Mahan) writes: > > In a previous article, rainer@boulder.Colorado.EDU (Rainer Malzbender) writes: >>In article <1991Apr02.174845.5076@lynx.CS.ORST.EDU> rudolpe@prism.CS.ORST.EDU (Eric Rudolph) writes: >>> >>>I need to know about how VPA* VMA* E* and AS* are related. I have one >>>timing diagram for them and a little chart that tells the relative >>>timings, but I need to know WHAT they do and how they relate in English. >>>Things like "what would happen if the device didn't assert VPA" and >>>"Why does the 68k assert VMA* and how does it relate to VPA*" stuff like >>>that.... I would be very grateful. I am designinga the famed speedup circuit >>>for the Amiga.... >> >>VPA, VMA, and E are used to interface to older 6800-style peripheral chips. >>E is a clock that is the CPU clock divided by 10. VPA and VMA mean "valid >>peripheral address" and "valid memory address" (I think - all my hardware >>manuals are at home). They basically inform the 68000 that it is talking >>to a 6800 peripheral. I could dig up the databook later, but I'm almost >>positive you don't have to worry about these signals at all if you're >>designing for the Amiga. On my 68000 designs I never use VPA and VMA; >>sometimes I use E if I need a slower clock. VPA*, VMA*, and E* are all used in synchronous communication. When the 68000 looks for DTACK* and does not receive it, it checks for VPA*. If VPA* is asserted then it now knows it is talking to a sychronous device. VMA* and E* are then used in communicating to the device. Also VPA* is used when an interrupt is auto-vectored. In other words if the vector number is not provided to the CPU (DTACK* will also not arive then) VPA* is asserted telling the CPU to look up the vector based on the interrupt level. - Mike
skipper@motaus.sps.mot.com (Skipper Smith) (04/09/91)
In article <1991Apr4.105321.12087@csusac.csus.edu> cs1598@athena.ecs.csus.edu writes: > VPA*, VMA*, and E* are all used in synchronous communication. When >the 68000 looks for DTACK* and does not receive it, it checks for VPA*. >If VPA* is asserted then it now knows it is talking to a sychronous >device. VMA* and E* are then used in communicating to the device. > > - Mike Technicality time: Actually, /VPA (or VPA* depending on your teacher) is checked prior to /DTACK. If they are asserted at the same time, /VPA will be used. However, somewhat obviously I hope, they should never be asserted at the same time. Everything else you said was not only correct, but said quite well. -- Skipper Smith | skipper@motaus.sps.mot.com Motorola Technical Training | 8945 Guilford Rd Ste 145 All opinions are my own, not my employers | Columbia, MD 21046
jms@tardis.Tymnet.COM (Joe Smith) (04/10/91)
In article <1991Apr2.220648.23079@colorado.edu> rainer@boulder.Colorado.EDU (Rainer Malzbender) writes: > ..., but I'm almost positive you don't have to worry about these signals >at all if you're designing for the Amiga. It's true that the expansion cards for the Amiga don't need to worry about VPA, VMA, and E signals. However, there are two CIA (Complex Interface Adapters, with counters, timers, and 8-bit parallel I/O) on the Amiga's motherboard that do need those signals. Hardware hackers have already found that simply doubling the CPU's clock does not work - the time-of-day clock stops working, the floppy disk step-in/step-out signal stops working, the parallel port stops working, the joystick and mouse stop working. All because the E signal needs to be correct. -- Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com BT Tymnet Tech Services | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-C51 | BIX: smithjoe | CA license plate: "POPJ P," (PDP-10) San Jose, CA 95161-9019 | humorous dislaimer: "My Amiga 3000 speaks for me."
cs1598@athena.ecs.csus.edu (Michael Noriega) (04/10/91)
In article <1991Apr9.165559.12876@motaus.sps.mot.com> skipper@motaus.sps.mot.com (Skipper Smith) writes: >In article <1991Apr4.105321.12087@csusac.csus.edu> cs1598@athena.ecs.csus.edu writes: >> VPA*, VMA*, and E* are all used in synchronous communication. When >>the 68000 looks for DTACK* and does not receive it, it checks for VPA*. >>If VPA* is asserted then it now knows it is talking to a sychronous >>device. VMA* and E* are then used in communicating to the device. >> >> - Mike > >Technicality time: Actually, /VPA (or VPA* depending on your teacher) is >checked prior to /DTACK. If they are asserted at the same time, /VPA will be >used. However, somewhat obviously I hope, they should never be asserted at the >same time. Everything else you said was not only correct, but said quite well. > Thanks for the correction Skipper. I am starting to work on my Senior Project for next semester and I planning on using the MC68000 and MC56001 so it behoves me to know the 68000 inside and out. > >-- >Skipper Smith | skipper@motaus.sps.mot.com >Motorola Technical Training | 8945 Guilford Rd Ste 145 >All opinions are my own, not my employers | Columbia, MD 21046 - Mike