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Re: SD I/O 1.8MHz resonator
Zanchius wrote:
Humm ... This adds another gremlin in the equation. I'm starting to regret ordering only the PCBs.That will work. 1.8432 MHz hits 9600 baud exactly. The 1.80 MHz resonator is actually 2.4% low (but it works anyway). Lee -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -- This email has been checked for viruses by Avast antivirus software. |
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Re: SD I/O 1.8MHz resonator
Zanchius wrote:
I would be comfortable in flipping a byte or two on the EPROM image, I managed to find a programmer that can burn 27256 chips so that also wouldn't be an issue.Hi Flavio, Download the EPROM source file at <> from the website at <>. In the .ASM or .LST file, search for "LD (ACE_BAUD),A". It occurs in two places. The first one sets the initial baud rate to 9600 (with a 1.8 MHz resonator or 1.8432 crystal). Change the byte at 01AE to whatever is correct for your crystal and desired baud rate. 01A5 21 80FF COLD_START LD HL,RC_TYPE 01A8 06 0F LD B,CS_CLR_LEN 01AA CD 100C CALL CLEAR_BLOCK ;DB 0 ;(RC_TYPE) ;DB 0 ;(RC_SOFT) ;DB 0 ;(RC_STEP) ;DB 0 ;(RC_CC) ;DB 0 ;(RC_HALT) ;DB 0 ;(RC_F0) ;DB 0 ;(RC_RST0) ;DB 0 ;(RC_HARD) ;DB 0 ;(RegPtr) ;DW 0 ;(ABUSS) ;DB 0 ;(IoPtr) ;DB 0 ;(RX_ERR_LDRT) ;DB 0 ;(RX_ERR_STOP) ;DB 0 ;(RX_ERR_OVR) 01AD 3E 0C LD A,12 <=== this sets 9600 baud! 01AF 32 8FFF LD (ACE_BAUD),A Or, if you're using the Z80-CPU card serial port, you can change the Z80-SIO card baud rate using this call: 080B CD CA0D PORT_SPEED CALL PRINTI 080E 0D0A2830 433D3936 DB CR,LF,"(0C=9600) BAUD:",EOS 0816 30302920 42415544 081E 3A00 0820 3A 8FFF LD A,(ACE_BAUD) 0823 CD F60D CALL PUT_BYTE 0826 CD 490D CALL SPACE_GET_BYTE 0829 D8 RET C 082A 32 8FFF LD (ACE_BAUD),A 082D CD F214 CALL ACE_SET_BAUD 0830 C9 RET Hope this helps! Lee -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -- This email has been checked for viruses by Avast antivirus software. |
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Re: SD I/O 1.8MHz resonator
bill rowe wrote:
Josh: does your serial code do autobaud - i forget? If so it would probably be fine.No; it doesn't autobaud. But there are two serial ports; one on the Z80-CPU board, and another on the Z80-SIO board. The one on the CPU board uses the 4 MHz resonator; so it will still work. It is fixed at 9600 baud; but would be 4800 baud if you used a 2 MHz resonator, or 19200 if you used 8 MHz etc. The 8250 UART on the Z80-SIO board uses the 1.8 MHz resonator. 18.432 MHz and 3.072 MHz happen to give you all the standard baud rates from 50-38.4Kbaud with negligible error. See the 8250/82C50/16C450 datasheet for details on how to calculate the baud rate constant for various frequencies. Lee -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -- This email has been checked for viruses by Avast antivirus software. |
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Re: SD I/O 1.8MHz resonator
Humm ... This adds another gremlin in the equation. I'm starting to regret ordering only the PCBs. But hey, there isn't any fun without problems to solve. I may have a handful of 1.8432MHz crystal oscillators in my stock so I'll give it a try. F? On Fri, 30 Apr 2021, 18:39 Mark Moulding, <mark@...> wrote:
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Re: SD I/O 1.8MHz resonator
Zanchius wrote:
Good morning all,Hi Flavio, Yes, I'm having trouble getting the 1.8 MHz resonators as well. Mouser quit carrying them, so I bought my last batch from Tayda2009 on ebay. But they seem to have gone out of business. As for the FJN3303 and FJN4303 transistors, I have enough for customers; but shipping to the UK is expensive. The frequency is critical to get the right baud rate. Changing from 1.8 to 2.0 MHz will change the baud rate from 9600 to 1066 baud. It will still work if you can set your Terminal program for such an oddball rate. A better solution is to get a 1.8432 MHz crystal, which is a standard frequency and fairly easy to find. Crystals don't have the internal capacitors, so you'll also need to add two 20pf capacitors, one from each side of the crystal to GND (the schematic in the manual shows these capacitors). Another option is to change the divisor in the 8250 UART. This can compensate for your 2 MHz resonator. But it means changing a byte in the EPROM, and burning another one. Lee -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -- This email has been checked for viruses by Avast antivirus software. |
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Re: Transistor replacements
Frank Palazzolo wrote:
I built my kit to do TTL-serial only, and I don't plan to use real RS-232 voltage levels.Q1 and Q4 (on the Z80MC Front Panel) are only needed for RS-232 serial. So they can be left out. :-) Another alternative would be to find a compatible N-channel andAn N-channel MOSFET (like a 2N7000 or BS170) might work for Q2 and Q3. Their base (gate) is pulled either high or low (so never left floating). The base of Q5 is driven by capacitor C5; so you need the base resistors to work. A P-channel MOSFET (BS250) might work if you added a gate-source resistor to insure that it turned it off. Or, you could leave it off -- without it, you can't reset the Z80 with the DTR line from the serial port. For an active part, it seems like you could find a match in a surface mount package, if you're willing to solder that to the top (or bottom, depending on the pinout).Right; there are lots of surface-mount alternatives. But watch the pinouts! Lee Hart -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -- This email has been checked for viruses by Avast antivirus software. |
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Re: Transistor replacements
Flavio Vinicius Spalato Zanchi wrote:
Lee,These pre-biased transistors are handy parts. They save parts, and thus save space on the PCB. They are bipolar, and so are not susceptible to static damage, and don't have parasitic "protection diodes" (which was useful for the RS-232 interface). It's unfortunate that you're in the UK. I have the transistors; but postage for a 1-ounce letter to the UK is over $5, and the minimum package postage is over $15. They also insist that envelopes be "flat". I tried to mail an LED in an envelope, and it arrived with chips knocked out of it! Lee Hart -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -- This email has been checked for viruses by Avast antivirus software. |
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Re: Transistor replacements
Lee, Many thanks for the reply. I'm absolutely sure that you and the community created the best design with what was available at the time. Once again I am out of luck. TME, being in Poland, and thanks to Brexit, doesn't ship to the UK for the time being. So I will take the risk and order the SMD equivalents (MMUN2212LT1G , NSVMMUN2112LT1G),? with a bit of effort I think I can fit them on the board. Flavio On Mon, 26 Apr 2021, 17:46 Lee Hart, <leeahart@...> wrote: flavio@... wrote: |
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Re: Transistor replacements
flavio@... wrote:
I am sourcing the components for the Z80MC, which have brought me to a halt trying to find the pre-biased transistors Q1-Q5 used on the front panel (FJN3303R, FJN4303R) and even their equivalents (NTE2358, NTE2357).? The TO92 versions all seem to be out of production... Are there any other equivalents that could be used instead? Glad if anybody could point me in the right direction.These "pre-biased" transistors with internal resistors have been around for decades, and there are hundreds of part numbers. When I designed them into the Z80MC, all the major distributors stocked them for a few cents each. I buy my PC boards and parts to go on them in batches; so I still have enough of the FJN3303R and FJN4303R transistors for kits, and to supply customers who bought the bare boards from me. If that's the case, let me know. :-) But the age of through-hole parts is coming to an end. Surface-mount parts are everywhere; but through-hole versions of the same parts are disappearing. Digikey and Mouser sold their remaining inventories to Rochester Electronics. Rochester is a good outfit; but they have a $250 minimum order. For a 3-cent part, that means buying >10,000! I added the NTE equivalents to my manual. NTE has long been a supplier of replacement parts for service and repair. They buy a standard part, add their own part#, and jack up the price. They maintain inventory, which costs money. So if you only need one, and don't care what it costs, they've got it! It doesn't help that manufacturers don't use generic 2Nxxx or 2SBxxx numbers any more; they hide them with their own "house" numbers, so you can't easily cross-reference them to other parts. When searching, use the term "pre-biased transistors" to find them. There are *lots* of equivalents (especially surface-mount); but they've made them hard to find. Octopart.com is a free search engine for electronic components. They'll show who has (or says they have) stock on parts such as these. At the moment, they list: NTE2357 NPN $1.20 each NTE2358 PNP $0.78 each -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -- This email has been checked for viruses by Avast antivirus software. |
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Re: Transistor replacements
Hi Josh, Unfortunately at least in their UK branches they are both not available and marked as obsolete. I've also looked at Farnell with the same result. gives a list of equivalents but I am not sure which would be better suited. Curiously enough, Amazon has it but it's a super inflated price, and I would rather pay ?0.50 than ?4.50 Flavio On Mon, 26 Apr 2021, 14:11 joshbensadon via , <joshbensadon=[email protected]> wrote:
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Transistor replacements
Hi there,
I am sourcing the components for the Z80MC, which have brought me to a halt trying to find the pre-biased transistors Q1-Q5 used on the front panel (FJN3303R, FJN4303R) and even their equivalents (NTE2358, NTE2357).? The TO92 versions all seem to be out of production... Are there any other equivalents that could be used instead? Glad if anybody could point me in the right direction. Cheers |
Lee Hart
Zanchius