To: Jefferson@Marketing@GRiD From: Strang Subject: Re: 422 connector Date sent: 08/26/89 5:31 PM Copies: Bailey it'sIn reply to the message of 08/25/89 4:01 PM from Jefferson@Marketing@GRiD: Judy The main reasons for using that 19 pin connector are consistency with past GRiD computers, physical size, and to discriminate that special serial port from normal IBM style COM serial ports. The part number for the connector is 2DE19, with a 2DE19P (P for Plug, a male connector) on the computer and a 2DE19S (S for Socket, a female connector) on the cable. Consistency: A serial port which is synchronous and isochronous capable and has balanced "RS-422" data and clock lines is a GRiD trademark of sorts. It was originally developed to support the GRiDLink Local Area Network. Every "GRiDLink" style serial port that GRiD has ever put on a computer (except GRiDServers) has used that 19 pin connector. While we are using the 85C30 USART instead of the 8274, this will still be a "GRiDLink" port in that it will be synchronous and isochronous cabable and will have balanced "RS-422" data and clock signals. There are a significant number of existing cables and customer applications out there that already have that 19 pin connector on them. I asked the Federal sales reps about changing away from the 2DE19 connector, and they said we had better have a pretty good reason before doing so. They would like to upgrade a bunch of Tempest applications from Tempest Compasses or 1307s to 1537s, and having a matching 2DE19 connector helps. Physical size: The 2DE19 connector is the same size as a DB9, yet has over twice as many pins. If one is cramped for connector space, that is useful. The GRiD Compass certainly was not cramped for connector space, so I'm note sure why they chose such a small connector for their serial port. Incidentally, while the 2DE19 connector is difficult to assemble due to it's small size, its harder than DB connectors to hurt once it's assembled, because of the plastic shield that protects the pins. It surns out to be much easier to assemble the female (2DE19S) connector if you thread the wire through the plastic shield, them crimp on the pins, then pull them back into place. Discrimination: "GRiDLink" style serial ports are significantly different from IBM style COM serial ports, and they are of course NOT software compatible. The 2DE19 connector is one way of symbilizing this difference and avoiding our customers thinking that the port will be "plug and play" for MS-DOS communication software. Even with the 2DE19, we still have occasional problems with customers thinking that it is a COM2 port on the 1307. From the flexibility and simplicity point of view, it would be real nice if we could use a connector with more pins on the 85C30 port. If we had 40 pins, we could bring all the data, clock, and signal lines for both channels out as balanced "RS-422" signals and dispense with some of the fancy switching circuitry I designed for the port. Anything between 19 and 40 pins would be some improvement, but it would require careful analysis and negotiation with development to decide how best to use the additional pins. We definitely should NOT use a DB25 connector for this port. There are too many DB25s on computers already, and look at the trouble it's caused for GRiD in the external floppy port. Will -------------------------------------------- Will, Is the 19 pin connector for the 422 required? As I understand (and I'm not sure I really do understand) this is a non standard connector and will require special cables. Can you please educate me on this matter? thanks - as always Judy