Polling communication system with priority control

• US 5,132,680 A
• Filed: 12/07/1989
• Issued: 07/21/1992
• Est. Priority Date: 12/09/1988
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Shinomiya, Tomohiro, Tezuka, Koji, Amemiya, Shigeo, Soejima, Tetsuo, Iguchi, Kazuo
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): WEISSMAN, PETER
• Application Number:
  US07/447,432
• Time in Patent Office: 957 Days
• Field of Search: 340/825.08, 340/825.5, 340/825.07, 340/825.51, 340/505, 340/518, 370/85.8, 370/95.2, 370/104.1, 364/200, 364/900
• US Class Current: 340/3.51
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling

Abstract

A communication system including a master station, a plurality of slave stations each for communicating with the master station, a two-way transmission line connecting the master station and the plurality of slave stations. Each of the slave stations sends a request for further communication with the master station, to the master station when its own slave station is allowed to communicate with the master station and its own slave station has the above request. The master station detects the request for further communication with the master station in a signal sent from a slave station, and memorizes the slave station from which the request for further communication with the master station is detected, until an allowance signal is sent to the slave station from the master station corresponding to the memorizing of the slave station. The master station has a cyclic address pointer which points to an address of a next one of the slave stations in a cyclic order when no slave station is memorized in the master station. The master station outputs the allowance signal to communicate with the master station to a slave station which is memorized in the master station or to a slave station the address of which is pointed to by the cyclic address pointer when no request is memorized in the master station.

Claims

1. A communication system, comprising:

a master station,

a plurality of slave stations each for communicating corresponding data with said master station; and

a two-way transmission line connecting said master station and said plurality of slave stations;

each of said slave stations includes at least

request sending means for sending a request for further communication with said master station appended to the corresponding data sent to said master station when said slave station corresponding thereto receives an allowance signal from said master station and said slave station corresponding thereto has the request for further communication;

transmitting means for sending the corresponding data upon reception of the allowance signal;

said master station includes at least;

request detecting means for detecting the request for further communication with said master station which is appended to the corresponding data sent from one of said slave stations;

request memorizing means for memorizing one of said slave stations from which the request for further communication with said master station is detected, until the allowance signal is sent from said master station to the one of said slave stations corresponding to the memorizing of the one of said slave stations;

cyclic address pointing means for pointing out an address of a next one of said plurality of slave stations in a cyclic order when no slave station is memorized in said request memorizing means; and

select control means for outputting the allowance signal to communicate with said master station either to one of said slave stations read out from said request memorizing means when at least one of said slave stations are memorized in said request memorizing means, or to one of said slave stations the address of which is pointed out by said cyclic address pointing means when no slave station is memorized in said request memorizing means.

2. A communication system according to claim 1, wherein said select control means outputs the allowance signal to communicate with said master station to one of said slave stations read out from said request memorizing means in the order the request is received by said master station when at least one slave station is memorized in said request memorizing means.

3. A communication system according to claim 1, wherein each of said slave stations further comprises self address detecting means for detecting the address of said slave station corresponding thereto in a signal received from said master station.

4. A communication system according to claim 3, wherein said request sending means comprises:

request bit generating means for generating a request bit indicating whether said slave station corresponding thereto has the request for further communication with said master station; and

sending means for sending the request bit, the address of said slave station corresponding thereto, and the data to be sent to said master station, when the address of said slave station corresponding thereto detected in said self address detecting means.

5. A communication system, comprising:

a master station;

a plurality of slave stations each for communicating corresponding data with said master station; and

a two-way transmission line connecting said master station and said plurality of slave stations;

each of said slave stations includes at least

request sending means for sending a request for further communication with said master station appended to the corresponding data sent to said master station when said slave station corresponding thereto receives an allowance signal from said master station and said slave station corresponding thereto has the request for further communication;

transmitting means for sending the corresponding data upon reception of the allowance signal;

said master station includes at least;

request detecting means for detecting the request for further communication with said master station which is appended to the corresponding data sent from one of said slave stations;

request memorizing means memorizing one of said slave stations from which the request for further communication with said master station is detected, until the allowance signal is sent from said master station to one of said slave stations corresponding to the memorizing of one of said slave stations;

counter means for counting a count number of successive cycles in which read-out operations of said slave stations from said request memorizing means are carried out, and for resetting the count number when the count number becomes equal to a predetermined number;

cyclic address pointing means for pointing out an address of a next one of said plurality of slave stations in a cyclic order either when no slave station is memorized in said request memorizing means, or when the number counted by said counter means becomes equal to the predetermined number;

select control means for outputting the allowance signal to communicate with said master station to one of said slave stations read out from said request memorizing means when at least one of said slave stations are memorized in said request memorizing means and the count number in said counter means is not equal to the predetermined number, and for outputting the allowance signal to communicate with said master station to one of said slave stations the address of which is pointed out by said cyclic address pointing means either when no slave station is memorized in said request memorizing means, or when the count number in said counter means is equal to the predetermined number.

6. A communication system according to claim 5, wherein said select control means outputs the allowance signal to communicate with said master station to one of said slave stations read out from said request memorizing means in the order the request is received by said master station when at least one slave station is memorized in said request memorizing means.

7. A communication system according to claim 5, wherein each of said slave stations further comprises self address detecting means for detecting the address of said slave station corresponding thereto in a signal received from said master station.

8. A communication system according to claim 7, wherein said request sending means comprises:

request bit generating means for generating a request bit indicating whether said slave station corresponding thereto has the request for further communication with said master station; and

sending means for sending the request bit, the address of said slave station corresponding thereto, and the data to be sent to said master station, when the address of said slave station corresponding thereto is detected in said self address detecting means.

9. A communication system, comprising:

a master station;

a plurality of slave stations each for communicating corresponding data with said master station; and

a two-way transmission line connecting said master station and said plurality of slave stations;

each of said slave stations includes at least

request sending means for sending a request for further communication with said master station appended to the corresponding data sent to the master station when said slave station corresponding thereto receives an allowance signal from said master station and said slave station corresponding thereto has the request for further communication;

transmitting means for sending the corresponding data upon reception of the allowance signal;

said master station includes at least;

request detecting means for detecting the request for further communication with said master station which is appended to the corresponding data sent from one said slave stations

request memorizing means for memorizing one of said slave stations from which the request for further communication with said master station is detected, until the allowance signal is sent to one of said slave stations corresponding to the memorizing on the one of said slave stations from said master station;

requesting address pointing means for pointing out one of the addresses of said slave stations memorized in said request memorizing means in a first predetermined order;

non-requested address pointing means for pointing out one of the addresses of said slave stations not memorized in said request memorizing means in a second predetermined order; and

select control means for outputting the allowance signal to communicate with said master station either to one of said slave stations the address of which is pointed out by said requested address pointing means when at least one slave station is memorized in said request memorizing means, or to one said slave stations the address of which is pointed out by said non-requested address pointing means when no slave station is memorized in said request memorizing means.

10. A communication system according to claim 9, wherein each of said slave stations further comprises self address detecting means for detecting the address of said slave station corresponding thereto in a signal received from said master station.

11. A communication system according to claim 10, wherein said request sending means comprises:

request bit generating means for generating a request bit indicating whether said slave station corresponding thereto has the request for further communication with said master station; and

sending means for sending the request bit, the address of said slave station corresponding thereto, and the data to be sent to said master station, when the address of said slave station corresponding thereto is detected in said self address detecting means.

12. A communication system according to claim 9, wherein the first and second predetermined orders each have a cyclic order.

13. A communication system, comprising:

a master station;

a plurality of slave stations each for communicating corresponding data with said master station; and

a two-way transmission line connecting said master station and said plurality of slave stations;

each of said slave stations includes at least

request sending means for sending a request for further communication with said master station appended to the corresponding data sent to the master station when said slave station corresponding thereto receives an allowance signal from said master station and said slave station corresponding thereto has the request for further communication;

transmitting means for sending the corresponding data upon reception of the allowance signal;

said master station includes at least

request detecting means for detecting the request for further communication with said master station which is appended to the corresponding data sent from on of said slave stations;

request memorizing means for memorizing one of said slave stations from which the request for further communication with said master station is detected, until the allowance signal is sent from said master station to one of said slave stations corresponding to the memorizing of the one of said slave stations;

counter means for counting a count number of successive outputs of allowances to communicate with said master station which have been given to said slave station memorized in said request memorizing means, and for resetting the count number when the count number becomes equal to a predetermined number;

requested address pointing means for pointing out one of the addresses of said slave stations memorized in said request memorizing means in a first predetermined order;

non-requested address pointing means for pointing out one of the addresses of said slave stations not memorized in said request memorizing means in a second predetermined order; and

select control means for outputting the allowance signal to communicate with said master station to one of said slave stations the address of which is pointed out by said requested address pointing means when at least one slave station is memorized in said request memorizing means and the count number in said counter means is not equal to the predetermined number, and for outputting the allowance signal to communicate with said master station to one said slave stations the address of which is pointed out by said non-requested address pointing means when no slave station is memorized in said request memorizing means, or when the count number in said counter means is equal to the predetermined number.

14. A communication system according to claim 13, wherein each of said slave stations further comprises self address detecting means for detecting the address of said slave station corresponding thereto in a signal received from said master station.

15. A communication system according to claim 14, wherein said request sending means comprises:

request bit generating means for generating a request bit indicating whether said slave station corresponding thereto has the request for further communication with said master station; and

sending means for sending the request bit, the address of said slave station corresponding thereto, and the data to be sent to said master station, when the address of said slave station corresponding thereto is detected in said self address detecting means.

16. A communication system according to claim 13, wherein the first and second predetermined orders each have a cyclic order.