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26

It's not dark magic, it's just that there is no hardware limit for 9600 bps to begin with. There are many factors at play here, it's just not about the UART chip. The speed depends on basically from these items: Design & marketing plans/specs of an IBM PC before hardware was designed CPU speed ISA bus speed between CPU and UART Disk transfer speed The ...


22

A tight polling loop can easily achieve a solid transfer speed of 11,520 bytes/second over a 115,200 baud serial link, even when using a moderately slow processor. Even if a processor can only run 250,000 instructions/second (which is pretty slow), it could afford to spend more than 20 instructions dealing with each byte. Disabling interrupts would likely ...


17

In more recent designs, since the mid-2000s I think, it became common to include "key" pins like this to reduce assembly errors. In most cases the pin removed was non-essential in the first place, eg. an extra ground pin or a no-connect. I think in this case it is a no-connect. In the case of COM headers, there are actually two different pinouts ...


13

Well, this is to be expected; the BIOS Data Area has only four slots for I/O addresses of serial ports, with slots for parallel ports immediately following. In the MEMORY.LST file from Ralf Brown’s, we can find the following entries0: MEM 0040h:0000h - BASE I/O ADDRESS OF FIRST SERIAL I/O PORT MEM 0040h:0002h - BASE I/O ADDRESS OF SECOND SERIAL I/O PORT ...


13

The BIOS list only contains addresses of up to four standard 8250-type COM ports found at boot at the standard addresses. It will not contain more than four ports, it will not contain any non-8250 type COM ports, and COM ports at non-standard addresses, such as PCIE COM ports, and USB COM ports which don't have an IO address to begin with. It will not ...


12

Just one example: The Trimble GPS receiver's (used on agricultural positioning systems, for example) proprietary TSIP protocol (roughly end of the century, so somewhat retro already) uses odd parity by default. Odd parity has one marginal advantage over even, at least for even bit-lengths: If you have the data input stuck at 0 or 1 (which is a probably more ...


11

I posted a comment on the reverse-engineering Q&A you linked before I realized it'd do better as an answer here. The answerer there found that googling Accom and Axial from your photo turns up a series of video editing controllers, and documentation for a DE-9 connector. If it's an editing controller running RS-422 over DE-9, it's almost certainly Sony 9-...


10

In addition to the fact that some serial-port adapter cables have a blocked off pin, I've seen boards and cards use two different pinouts. On a DB-9 male, the pins are numbered 1 2 3 4 5 6 7 8 9 but on the 10-pin connector the pins are numbered: 2 4 6 8 10 1 3 5 7 9 I've seen some cables which connect pin 1 to 1, 2 to 2, etc. but I'...


7

The OS itself has no terminal application by default. There have been multiple terminal programs available in earlier times, though. The most prominent and easy to use might have been zTerm. Double-click with shift, choose port, set serial parameters from the popup-menus at the window bottom and you're good to go. Search for zTerm in your favourite old Mac ...


6

Even parity has the advantage of making all zeroes a valid state and for even word lengths also makes all ones a valid state. Odd parity has the advantage of making all valid states contain at least one bit set. I don't know of asynchronous serial peripherals that used odd parity, since async signalling protocol guarantees that every byte will have a start ...


6

The BIOS data area only has room for addresses of four com ports, at 40:00 through 40:07. More serial ports would be driven by some device driver with some other place to store the address(es) and IRQ(s).


6

Options: (1) Googling "Accom axial" finds various people who bought it, made Youtube reviews etc. If these are not you, contact them and see if they have details. (2) As has been mentioned in the comments, you need a RS422 (not RS232) adapter, e.g. to USB. The cheapest I found after a quick search is 20 EUR. (3) You can often find the serial ...


5

I had the problem that the data transfer got interrupted after 73 Bytes of data. The HP48's Kermit Server always terminated with 'Protocol Error'. Smaller ASCII-Objects, <= 72 bytes, however were transferred correctly. My solution for ckermit 9.0.305, compiled from the source C-Kermit “Daily” Source-Code Archive mentioned above, is to set an additional ...


5

TL;DR The various issues are due clocking. In part by using 'unconventional' ways of clock handling but as well by simply violating specs. Main points are SIO (and in fact CPU) are not static designs but dynamic. As such they requite certain clock speeds and relation. Clocking the system at 10 Hz violates a whole bunch of rules Minimum system clock speed ...


4

The Wikipedia article for RS-422 (linked to in @lvd's comment) links to a page on the Sony 9-pin protocol. In the references for that article is a link to what appears to be a pretty thorough description of the protocol. That said, the product information for the Shogun Studio 2 states that RS422 (9-pin) support "will be added in future Firmware ...


4

As far as I’m aware, it isn’t. I don’t remember any Linux software capable of connecting to LapLink; the latter was commonly mentioned because the cable provided with it could be used with a variety of tools. DOS-to-Linux connections with null-modem cables usually involved PLIP, SLIP or PPPD rather than LapLink-style tools.


3

Thank you for all the answers. Turns out that the 10th pin is indeed "fake", it's not connecting anywhere. So the answer is yes, I could drill a hole on the connector. However, there are two different types of serial connectors, and they're not interchangeable. A 9 pin cable will not work correctly. So much for standards, thank you, PC industry! ...


1

Instead of drilling, you may be able to clip off the mating pin with small wire cutters. If the pinout is suitable, this will be easier. Of course it damages the connector on the motherboard if it's not. For testing you can also bend the offending pin down and push the connector part way on. A stackable header can be used between the cable and motherboard, ...


1

Parity is generally used with unidirectional transmission where a recipient who observes an error would be able to take into account that the received data might be incorrect. When used with teleprinters, a parity error would often cause an "error" character to be printed in place of some other character. If, for example, there was a newswire ...


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