ld@sri-unix (09/10/82)
Is there an ANSI standard, or any other standard, that specifies how long a break `character' is supposed to be (200 ms? 250 ms?). Logically, I understand why it should be greater than 200 ms, but I cannot find any documentation that explicitly spells this out (it seems to me that somewhere in my library, which has been neatly filed in the attic, I read a document that stated it had to be greater than 200 ms.) The reason I ask is because some of our data comm people want to specify that a break is two character-times in duration (very short at 9600 baud). This could cause uucp to burp, because it sends break characters to indicate speed changes. If an indial line is 110 baud, and a 9600 baud sender transmits a 2 character break, it will look like a hiccup to the receiver. Before I go to battle with the data comm staff at HP, I would like to have some ammunition. Thanks, Larry Dwyer Hewlett Packard Co. ucbvax!hpda!ld
taylor (09/14/82)
References: hpda.229 VERY interesting question. I checked my only 3 manufacterer-independent references (Doll's Data Communications, Martin's 'Tech. Aspects of Data Comm.", and McNamara's "Tech. Aspects of Data Comm." - Martin's is "Telecommunications and the Computer"), and could not even find a 'normal' break or interrupt defined! The 'long space' is pretty clearly defined for telco (modem) purposes as 1.5 to 4 seconds in various places, so the normal break must be much shorter. I've seen the range of 200 msec. in common usage, but I does not seem to be defined by either EIA or ANSI. I think that the two-character width definition is definitely unacceptable, and I can think of absolutely no basis for it (other than ease of terminal manufacturing.) I can think of several places it could cause problems. (For as close as I can find to an industry standard, the vt-100 Users Guide defines break as .2333 sec. +/- 10% and long break as 3.5 sec. +/- 10%. Page 37) Steve Taylor NC Educational Computing Service (919) 549-0671