Here's an HP description from http://www.bitsavers.org/pdf/hp/9000_dio/98642_HP- DIO_Four_Channel_Mux_ERD_Sep84.pdf (PDF page 24) "The PHI signal is output from the Z80 clock driver circuitry, which is a schottky clamped circuit using a PNP-NPN transistor (push- pull) pair to obtain the required current and waveform to drive the Z80 devices. " Probably very similar to the Z80 clock driver shown here: http://www.80bus.co.uk/pages/gemini/documentation/GM813_Circuit.pdf --Chuck

On 1 Jul 2012 at 18:37, Oliver Lehmann wrote: Done in discretes--the output of IC37e to TP4 at the Z80A is probably very close to what's under the blue goo on that hybrid chip. It should be fairly simple to verify. The input to the clock driver should show about 220 ohms to the Vcc connection and about 710 ohms to the ground connection. I suspect that HP didn't deviate too far --Chuck

On 1 Jul 2012 at 22:10, Oliver Lehmann wrote: Unless there's an external pullup resistor, I can't imagine that this is an OC output or that the drive is capacitively coupled Did you try the diode (high voltage) setting on your ohmmeter? --Chuck

Is it not plausible that 330 ohms to ground represents 327 ohms to Vcc plus three ohms Vcc-to-GND? /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mouse at rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B

Well, it's unlikely to be a simple three ohms. However, it easily could represent the effective resistance of the rest of the chip - or, more likely, the voltage dropped as small amounts of current leak through various paths, translated into a resistance measurement. Or, again depending on the details of the meter technology and how the measurement is done, it could be that the 327 ohm measurement does not represent 327 ohms of resistance but rather the forward drop of one of that input's protection diodes. /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mouse at rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B

Does 'n measurable ohm' mean a short (0 ohms) or open (infinte, overrange, etc)? If the otuptu is a totem pole circuit, or a PNP/NPN complementary driver with no pull-up resisotrs, and built from discrete compoennts so no parasitic diodes, is it certain that an ohmmeter iwll turn on at elast on of the transisotrs? I don't think it is. -tony

Mouse <mouse at rodents-montreal.org> wrote: Why? This header lines was put by my MUA and RFC5322[1] specifies: The "Message-ID:" field contains a single unique message identifier. The "References:" and "In-Reply-To:" fields each contain one or more unique message identifiers, optionally separated by CFWS. [...] The "In-Reply-To:" and "References:" fields are used when creating a reply to a message. They hold the message identifier of the original message and the message identifiers of other messages (for example, in the case of a reply to a message that was itself a reply). The "In-Reply-To:" field may be used to identify the message (or messages) to which the new message is a reply, while the "References:" field may be used to identify a "thread" of conversation. When creating a reply to a message, the "In-Reply-To:" and "References:" fields of the resultant message are constructed as follows: The "In-Reply-To:" field will contain the contents of the "Message-ID:" field of the message to which this one is a reply (the "parent message"). If there is more than one parent message, then the "In-Reply-To:" field will contain the contents of all of the parents' "Message-ID:" fields. If there is no "Message-ID:" field in any of the parent messages, then the new message will have no "In- Reply-To:" field. The "References:" field will contain the contents of the parent's "References:" field (if any) followed by the contents of the parent's "Message-ID:" field (if any). If the parent message does not contain a "References:" field but does have an "In-Reply-To:" field containing a single message identifier, then the "References:" field will contain the contents of the parent's "In-Reply-To:" field followed by the contents of the parent's "Message-ID:" field (if any). If the parent has none of the "References:", "In-Reply-To:", or "Message-ID:" fields, then the new message will have no "References:" field. [1]: http://www.rfc-editor.org/rfc/rfc5322.txt

The only wierd thing is some of the MIDs are comma-delimited, others not.

Mouse <mouse at rodents-montreal.org> wrote: This is then probably "my fault". My MUA just copied the References: which where already present and didn't "fixed" them. But - there is no paragraph in the RFC about fixing wrong headers ;) The "References:" field will contain the contents of the parent's "References:" field (if any) followed by the contents of the parent's "Message-ID:" field (if any). This is exactly what my MUA did - there is nothing about "...will contain the _fixed_ contents of the..." ;) And if your MUA is not able to handle the References header with comma and/or without - you are not able to read old emails written until RFC 5322 came out and thus having "," in there References header? If this would be my MUA, I would start complaining to it as it should have some sort of fallback plan in case a message arrives which is compatible to older RFCs. You probably can't make sure that all users in the world will immediatly switch to MUAs always compatible to the latest RFCs - you'll always have MUAs around which are not 100% compatible to the latest but to an older version of RFC (or to no RFC at all). Probably there should be a "Compatible-with:" header.......... Expecting every MUA to be compatible only to the latest RFC is a little bit naive - eh? Instead of tilting at windmills, save your time ;)

Mouse <mouse at rodents-montreal.org> wrote: Input -> VCC 322 Ohm Input -> GND 319 Ohm VCC -> Input 327 Ohm GND -> Input 330 Ohm Output -> VCC 5.23 MOhm Output -> GND 5.20 MOhm VCC -> Output 11.21 MOhm GND -> Output 11.20 MOhm

On 07/02/2012 01:24 PM, Chuck Guzis wrote: I haven't gone and checked, but I do recall pretty clearly that they specify a 330 ohm pullup on the clock line of a Z80, not 10K. -Dave -- Dave McGuire, AK4HZ New Kensington, PA

On 07/02/2012 01:34 PM, Dave McGuire wrote: All the circuits (including the Zilog manuals) I've seen use a 330 ohm or CMOS (rail to rail drive), or something like the 75452 drivers. The key thing is the clock must get to 4.75V nominal (4.4V minimum) with a reasonable rise time and fall times for the clock speed. Most TTl will not go much above 3.4-3.6V without help (pull up). Allison

On 1 Jul 2012 at 18:13, Dave McGuire wrote: Yup--you'd think that a 74S04 would have done the trick. But the Zilog manual cited shows pretty much the same thing--the input feeding a resistive divider to drive a PNP-NPN "totem pole" combination. The only really significant difference is that Zilog uses a 10K pullup on the output. So I'm guessing that the blue lump is very much like that. --Chuck

---snip--- Some of the app notes from the manufacture were wrong as well. I found an error in one of the notes for the 4040 Intel part. The reset was inverted relative to the original 4004 and needed an inverter to match the 4001 and 4002. They'd place a transistor between the 4040 and the other chips. The problem was that the 4040 would start running for 2 or three cycles before the 4001s were released. It wouldn't always reset right. In the app note, they said to put 3 or 4 NOPs at the begining of the code. This work most times but failed on about 5-10% of the boards I worked on while at Intel. It just require changing the order, release the 4001s first then the 4040. Dwight

On Mon, 2 Jul 2012, Chuck Guzis wrote: and the current inventory quantites for those were also negative?

On 07/02/2012 02:33 AM, Oliver Lehmann wrote: I suppose so! :-) -Dave -- Dave McGuire, AK4HZ New Kensington, PA