JPS6253049A - Modem interface switching system - Google Patents

Abstract

PURPOSE:To simplify control of changeover of many MODEM interfaces by using an ER signal representing the ready state of a data terminal device as a changeover command signal. CONSTITUTION:When the ER signal 1a representing ready state of a data terminal device rises, a reception circuit 2 generates a rising detection signal 2a and a changeover control circuit 3 holds the changeover signal 3a to 0 by using the signal. The MODEM interface is connected to an HOST 1 during this period. When the ER signal 1b rises next, a detection signal 2b is generated similarly and the circuit 3 holds the changeover signal 3a to level 1. The MODEM interface is connected to an HOST 2 during this period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is applicable to a modem/interface switching system, especially an HO
This invention relates to a modem interface switching method that performs all switching from ST.

[Conventional technology]

In the conventional modem interface switching method, a dedicated switching instruction signal line is provided, and switching is controlled by a monitoring device or the like on the HOST side.

[Problem that the invention seeks to solve]

The above-mentioned conventional modem interface switching method requires a dedicated switching instruction signal line, so especially when switching a large number of modem interfaces individually, it is necessary to provide separate switching instruction signal lines or to use a single switching instruction signal line. Cut 'I18
It was necessary to instruct the switching line in coded data on the signal line, and the control method was often complicated.

[Means for solving problems]

The modem interface switching method of the present invention includes two systems)
108 T Karaso 11. a receiving circuit that detects a rising edge of an ER multiplied signal indicating a ready state of a data terminal on a modem interface and outputs a rising detection signal; and a switching control circuit that controls switching of an interface switching circuit based on the rising detection signal. An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The modem interface signal from H (JST) is connected to the modem via the break contacts of switches Sl to Sn of switching circuit 1. Similarly to n1, the modem interface signal from HOST Connected to modem via.

)10sT 1 OER signal 1 from Onihi HOST 2
A and lb are branched and input the received image-1) 2 VC.

When impedance matching is applied to the receiving circuit 2, the same i′CE
R missing issue la, 1bo rising, all detected, so n-f:
'n rising edge; is input to the switching control circuit 3 as detection signals 2a and 2b.

When the switching control circuit 3 receives the rising detection signal 2ai, the switching signal 3a'k is held on and the rising edge detection signal 2ai is held.
When the switch 1g is set to 0", the switch 1g is controlled to be held at 0" when the switch 1g is set to 0", the switch Sl, Sn & go of the switching circuit 1, the break contact side, that is, F
5TJt l side, switching signal 3a is 11
'', the switches Sl and S are switched to the make contact side, that is, the HOST#2 side VC connection, so that the modem interface receives the H (JSTVC Switching over.

Next, the entire operation of the embodiment shown in FIG. 1Y will be explained.

FIG. 2 is a time chart illustrating the switching control circuit of Embodiment 9 shown in FIG. 1.

When ER[1a rises, a rising detection signal 2a is generated by the received image 'NZ2, and from this nVc, the switching control circuit 3 holds the switching signal 3a at 10''.

During this period, the modem interface is
The state is K-connected.

Next, when the ER signal 1b rises, a rising detection signal 2b is generated in the same way, and the switching control circuit 3 holds the switching signal 1g 33 at "1" (r). During this period, the modem interface is set to HOST'2. The state follows.

Even if ER1i No. 1a falls, the switching state is not affected.

ERjN lb has already started up.
When the R store number 1a rises, a rise detection signal 2a is generated, and the switching control circuit 311ff switches the switch control signal 3a to "0".
Make it.

Therefore the modem interface Fir-4USi'l
! '<: Kiribōseiza nru.

〔Effect of the invention〕

By using the modem interface switch of the present invention as an ER input signal, a dedicated switching instruction line is no longer required, and it is particularly useful for multiple modem interfaces. The effect of this is that the control JI, which requires switching for each switching, is simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 shows the structure of the embodiment shown in FIG. , is the ninth time chart explaining the zero conversion control operation. l...Switching circuit, 2...Receiving circuit, 3...
・Switching control circuit, 1a, lb... ・ER [No.,
2a, 2b...Rise detection signal, 3a...
・Switching signal, S1-S...Switch.

Claims (1)

[Claims] In a system where one modem interface is switched to two HOST systems, each HOST
A receiving circuit detects the rising edge of an ER signal indicating a ready state of a data terminal on a modem interface outputted from the ST system, an interface switching circuit switches the modem interface to the HOST system where the ER signal rises, and detects this switching state. 1. A modem interface switching method comprising: a switching control circuit that maintains a switching control circuit;