Overview

The X.3 PAD is a facility typically provided by the operator of an X.25 packet switched network that provides dial up access by ASCII terminals to the network. A protocol called X.28 allows the ASCII terminal to request that the PAD place a virtual call to some selected host on the network. The resulting virtual circuit is then used to link the ASCII terminal and the host. The protocol between the PAD and the host is called "X.29".

The factory PADF provides an object, the "padpeer", that holds an X.25 circuit key {(x25)} and behaves sufficiently like a level 3 circuit to support a session between an ASCII terminal connected to an X.3 PAD and the program designed to use a level 3 circuit.

PADF alternatively provides an object that may be connected to a switcher branch and together serve the function of pad and ASCII terminal. With one each of these PADF yields at opposite ends of an X.25 circuit a branch of a context may serve as a terminal on a remote KeyKOS. In this configuration function such as screen mode is lost because X.3 does not support such.

The padpeer is the KeyKOS facility that provides the host X.3 function. It operates at the end of an X.25 circuit in a KeyKOS host to adapt the X.3 protocol to KeyKOS programs designed to connect to terminals.

SYS.PADF(0;SB,M,SP=>0;,,,CO);
CO(LCN,IDENT;X25CK,SEG,FIN=>0;SIK,SOK,CCK) produces a module that serves as the peer to some X.3 pad located at the other end of the X.25 circuit represented by the key X25CK.

SEG must be a write key to a segment in which an activity indication is kept by instances of PADF yields. The newly created module will store into SEG at locations 16*LCN thre 16*LCN+15. No other use is made of either SEG or LCN.

Upon disolution of this module FIN will be forked thus: FIN(0,(1+109+128,ident);) where ident right truncated or right zero padded as necessary.

PADF(1;SB,M,SB=>0;,,,CO); CO(0;X25CK,CCK=>0;SIK,SOK) produces a module that serves as a combination pad and dialed ASCII terminal. Presumably X25CK has been produced by a call on an X25CONTROL key to place an X25 SVC. The yield of SWITCHER(0;=>0;CCK,SIK,SOK) provides a suitable key CCK.

A single line consisting of "clear" and sent with a PF2 (no CR) causes the call to be cleared and the module to be deleted.

The module buffers few characters and deletes itself upon clearing of the call or disappearing of the circuit key.