27c256 | 4K81H | 68HC11A1 | 68HC11P1 | 68hc24 | 68HC711E9 | 68HC811 | 8255 | A2D | ADC | ADC12138 | Am85C30 | BRCLR | Buffalo | CMOS | EEPROM | EPROM | Ethernet | EVB | EVBU | HC11E1 | HC11E9 | HC711E9 | Horray | ImageCraft | IRQ | Keypad | LCD | MC68HC11D0FN | MC68HC11E1CFU3 | MC68HC11F1 | MC68HC711E9 | MC68HC711E9CFN2 | Microcore11 | Microstamp11 | Minikit | NVRAM | PSD | PSD8xx | PSD9xx | PT1000 | RS232 | RTS | RXD | SPI | SRAM | TXD | Watchdogs | XIRQ

I want to interface 8255 (Intel's PPI Programmable Peripheral interface) with Motorola's 68HC11. Has any one successfully interfaced 8255 to 68HC11 CPU. I tried to interface 8255 to 68HC11 but it doesnot seem to work since timings seem to be different. 8255 data sheet says that CS (chip select) should be active before WR* signal, whereas 68HC11 address is latched in second half of E clock cycle. Hence in 68HC11 system, the CS signal from the address decoder is not wide enough. Thanks and Regards. CHITRA PACE Minmax Electronics, Bangalore India.

(You need to be a member of m68hc11 -- send a blank email to m68hc11-subscribe@yahoogroups.com )

The buss cycles of the Motorola and Intel busses are fundamentally different. You have five choices that I see -- 1. Don't try it, use a Motorola 6821 instead. 2. Assemble enough external logic (Perhaps a small PAL) to synthesize the Intel bus timing. See the 8255 data sheet for timing requirements. You may be able to find some application notes at the Moto web site with examples of how to do this. 3. Use latches and bus receivers to generate I/O ports. 4. Use shift registers and the SPI to generate I/O ports if speed is not critical. 5. Attach a WSI PSDxxx Peripheral System Device and use its discrete I/O pins. You also gain a bunch of memory resources. Try http://www.st.com/stonline/prodpres/memory/psd/html/psd_idx.htm . Good luck, Bob Smith --- Avoid computer viruses, Practice safe hex --- -- Specializing in small, cost effective embedded control systems -- Robert L. (Bob) Smith Smith Machine Works, Inc. 9900 Lumlay Road Richmond, VA 23236 804/745-1065 ----- Original Message ----- From: <> To: <> Sent: Saturday, May 04, 2002 6:54 AM Subject: [m68HC11] 68hc11 and 8255 > > I want to interface 8255 (Intel's PPI Programmable Peripheral interface) with Motorola's 68HC11. Has any one successfully interfaced 8255 to 68HC11 CPU. I tried to interface 8255 to 68HC11 but it doesnot seem to work since timings seem to be different. 8255 data sheet says that CS (chip select) should be active before WR* signal, whereas 68HC11 address is latched in second half of E clock cycle. Hence in 68HC11 system, the CS signal from the address decoder is not wide enough. > > Thanks and Regards. > > CHITRA PACE Minmax Electronics, Bangalore India. > > To unsubscribe from this group, send an email to:

(You need to be a member of m68hc11 -- send a blank email to m68hc11-subscribe@yahoogroups.com )

Hi Chitra, > I want to interface 8255 (Intel's PPI Programmable Peripheral > interface) with Motorola's 68HC11. Has any one successfully > interfaced 8255 to 68HC11 CPU. I tried to interface 8255 to > 68HC11 but it doesnot seem to work since timings seem to be > different. 8255 data sheet says that CS (chip select) should > be active before WR* signal, whereas 68HC11 address is > latched in second half of E clock cycle. Hence in 68HC11 > system, the CS signal from the address decoder is not wide enough. I don't know if it is of any help, but we have interfaced the HC16 to an 82C55 and it worked fine. What I don't know is if the HC11 has a /DS (data strobe signal). We used an inverter to generate a W/R from the R/W signal. Then a 74HC32 to generate the /8255W and /8255R signals: /8255W = R/W | /DS /8255R = W/R | /DS Bfn, Bob Furber __________________________________________________________ Connect your micro to the internet the easy way www.microcommander.com Microcontroller with an obscenity of I/O & features ..in a small footprint www.steroidmicros.com __________________________________________________________

(You need to be a member of m68hc11 -- send a blank email to m68hc11-subscribe@yahoogroups.com )

There is an example of such an interface on: http://www.ee.vt.edu/cel/datasheets/pcim201.pdf John Beatty wrote: > > I want to interface 8255 (Intel's PPI Programmable Peripheral interface) with Motorola's 68HC11. Has any one successfully interfaced 8255 to 68HC11 CPU. I tried to interface 8255 to 68HC11 but it doesnot seem to work since timings seem to be different. 8255 data sheet says that CS (chip select) should be active before WR* signal, whereas 68HC11 address is latched in second half of E clock cycle. Hence in 68HC11 system, the CS signal from the address decoder is not wide enough. > > Thanks and Regards. > > CHITRA PACE Minmax Electronics, Bangalore India. > To unsubscribe from this group, send an email to:

(You need to be a member of m68hc11 -- send a blank email to m68hc11-subscribe@yahoogroups.com )

It is a PITA. Make sure that the device the 68HC11 is reading presents the data long enough for the 68HC11 to read it. I had a very very major problem reading a Intel CAN chip with a 68HC11. It was a know problem with the CAN chip since it had a fast read register that held the contents of the last address read on the CAN chip so you read the address then got the results from the fast read register. That was a long time ago and thing may be different now. But If I remember right the 68HC11 has no way to generate the wait signal for the Intel bus. Good luck Gordon Gordon Couger Stillwater, OK www.couger.com/gcouger ----- Original Message ----- From: "Robert Smith" <> To: <> Sent: Saturday, May 04, 2002 8:15 AM Subject: Re: [m68HC11] 68hc11 and 8255 : The buss cycles of the Motorola and Intel busses are fundamentally : different. You have five choices that I see -- : : 1. Don't try it, use a Motorola 6821 instead. : : 2. Assemble enough external logic (Perhaps a small PAL) to synthesize the : Intel bus timing. See the 8255 data sheet for timing requirements. You may : be able to find some application notes at the Moto web site with examples of : how to do this. : : 3. Use latches and bus receivers to generate I/O ports. : : 4. Use shift registers and the SPI to generate I/O ports if speed is not : critical. : : 5. Attach a WSI PSDxxx Peripheral System Device and use its discrete I/O : pins. You also gain a bunch of memory resources. Try : http://www.st.com/stonline/prodpres/memory/psd/html/psd_idx.htm . : : Good luck, Bob Smith : : : --- Avoid computer viruses, Practice safe hex --- : : -- Specializing in small, cost effective : embedded control systems -- : : : Robert L. (Bob) Smith : Smith Machine Works, Inc. : 9900 Lumlay Road : Richmond, VA 23236 804/745-1065 : : : : ----- Original Message ----- : From: <> : To: <> : Sent: Saturday, May 04, 2002 6:54 AM : Subject: [m68HC11] 68hc11 and 8255 : : : > : > I want to interface 8255 (Intel's PPI Programmable Peripheral interface) : with Motorola's 68HC11. Has any one successfully interfaced 8255 to 68HC11 : CPU. I tried to interface 8255 to 68HC11 but it doesnot seem to work since : timings seem to be different. 8255 data sheet says that CS (chip select) : should be active before WR* signal, whereas 68HC11 address is latched in : second half of E clock cycle. Hence in 68HC11 system, the CS signal from the : address decoder is not wide enough. : > : > Thanks and Regards. : > : > CHITRA PACE Minmax Electronics, Bangalore India. : > : > : > : > To unsubscribe from this group, send an email to: : > : > : > : > : > : > : > : > : : : : To unsubscribe from this group, send an email to: : : : : : : : :

(You need to be a member of m68hc11 -- send a blank email to m68hc11-subscribe@yahoogroups.com )