JPH02301853A - Externally connected printer sharing system - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of such a printed result that plural output data are mixed in a printed output with an externally connected printer sharing system by providing a function which makes a host computer impossible to use the external printer while another host computer uses the printer until the another host computer declares the completion of the use. CONSTITUTION:Host computers 1 and 2 are respectively connected with an external printer 3 through a common bus 4. A function which makes one computer impossible to use the printer 3 while the other computer uses the printer 3 until the other computer declares the completion of the use even when the bus 4 is released, is provided. Therefore, the output of one computer to the printer is not mixed with the output data of the other computer and occurrence of such a printed result that output data of plural computers are mixed in the final printed output is eliminated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an externally connected printer sharing system in which a plurality of host computers (personal computers, etc.) control and share one printer using the same bus. It is something.

[Prior Art] Conventionally, as a means for realizing the above-mentioned J:Una system, Swall Compul, cr System l has been used.
n1. crl'++cc (referred to as L:J-Fscs+). SCSI allows multiple devices to be connected on the same bus, typically using a combination of one post computer and multiple post computers or external devices. You can also create a system that uses just one device.

[Problems to be solved by the invention] However, when a plurality of host computers share a printer device using the SC3I, there are the following drawbacks.

When a certain post-computer outputs to a printer, it first checks to see if the bus is free, and if the bus is free, connects the buses and sends data in units of output, such as one line or one page, to the printer. Turn off the bus once. Printing is performed by repeating this operation, but in such a case, the printer has no way of knowing which postcomputer is currently sending data to itself, so after it empties the tH4 bus, it Post combination; 1-
- If you connect a data bus to send data to a printer, the printer will print it. Therefore, there is a possibility that the finally obtained print result will be a mixture of a plurality of output data.

[Means (and operations) for solving the problem] According to the invention, when using a certain postcomputer or an external printer, even if the bus By providing a function that prevents other post computers from using the printer even if the printer is released, this prevents the output results from being mixed with output data from other computers. be.

[Example 1] Figures 1 to 4 show examples of the present invention, and the present invention will be described in detail below based on the drawings. FIG. 1 is a system configuration diagram in which a bus is shared, and a host computer 1, a host computer 2, and an external printer 3 are connected by a shared bus 4. In FIG. FIG. 2 is a block diagram of the post computer 1 and the post computer 2, which are similar to a general personal computer. FIG. 3 is a block diagram of the external printer. FIG. 4 is a flowchart 1 of the print control procedure according to the embodiment of the present invention.

Hereinafter, the printing control procedure of the present invention will be explained according to the flowchart of FIG. First, when the boss 1-computer 1 wants to print on the printer, it connects the bus through Sl and sends a command [- to declare the start of use to the printer in S2.

When the printer receives the start declaration command 1-, it stores it in its own RAM+3. POS] - Computer 1 once disconnects the bus at S3, connects the bus again at S4, sends a message to line S51, and disconnects the S6 bus. This S
Steps 4 to 1 of S6 continue until S7 data is completed. At this time, since the bus is open from S6 to 34, the post computer 2 can send data to the printer, but the host I/computer 1 is in use in the printer's RAM+3. The printer rejects this because the stator is stored. When the data output from the host 1 to computer 1 currently in use is completed in S7, the bus is connected in S8, and in S9 it is declared that the use of the printer is finished, and the SIO bus is disconnected. Upon receiving this declaration of completion of use, the printer clears the status of Boss 1 to Computer 1 in its RAM+3 indicating that it is in use, and returns to a state where anyone can use it.

[Effects of the Invention] As explained above, according to the present invention, when using multiple host computers or one external printer, there is no possibility that the output data of each printer will be mixed together, and the printing results will be as if they were printed on one printer. The same effect as having one printer per computer can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the external printer sharing system of the present invention, Fig. 2 is a block diagram of the host computer, Fig. 3 is a block diagram of the printer, and Fig. 4 is a diagram showing the printing control procedure. -1. I... Post combination coater 1 2... Host combination coater 2 3... External printer 4 - Shared bus 5... CPU 6... ROM 7... RAM 8 ... Display section 9 ... Operation section 10 ... External storage device 11 ... CPU 12 ... ROM 13 ... RAM 14 ... Printing section

Claims (1)

[Claims] 1. In a system where multiple host computers and an external printer are connected on the same bus, while a host computer is using the printer, even if the bus is released during that time, the host computer An externally connected printer sharing system characterized by providing a function that prevents other host computers from using the printer until the host computer declares that the use of the printer has ended.