SCHEDULE 13G  
  
Amendment No. 0  
Premisys Communications Incorporated  
Common Stock  
Cusip # 740584107  
 
 
Cusip # 740584107  
Item 1:	Reporting Person - FMR Corp.  
Item 4:	Commonwealth of Massachusetts  
Item 5:	120,400  
Item 6:	0  
Item 7:	2,667,400  
Item 8:	0  
Item 9:	2,667,400  
Item 11:	11.089%  
Item 12:	HC   
  
  
 
 
Cusip # 740584107  
Item 1:	Reporting Person - Edward C. Johnson 3d   
Item 4:	United States of America  
Item 5:	0  
Item 6:	0  
Item 7:	2,667,400  
Item 8:	0  
Item 9:	2,667,400  
Item 11:	11.089%  
Item 12:	IN   
  
 
 
Cusip # 740584107  
Item 1:	Reporting Person - Abigail P. Johnson   
Item 4:	United States of America  
Item 5:	None  
Item 6:	None  
Item 7:	2,667,400  
Item 8:	None  
Item 9:	2,667,400  
Item 11:	11.089%  
Item 12:	IN   
  
 
 
SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS  
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)  
  
  
Item 1(a).	Name of Issuer:  
  
		Premisys Communications Incorporated  
  
Item 1(b).	Name of Issuer's Principal Executive Offices:  
  
		48664 Milmont Drive,    
		Fremont, CA   94538  
  
Item 2(a).	Name of Person Filing:   
  
		FMR Corp.  
  
Item 2(b).	Address or Principal Business Office or, if None, Residence:  
  
		82 Devonshire Street, Boston, Massachusetts  02109  
  
Item 2(c).	Citizenship:  
  
		Not applicable  
  
Item 2(d).	Title of Class of Securities:  
  
		Common Stock  
  
Item 2(e).	CUSIP Number:    
  
		740584107  
  
Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b) and the  
person filing, FMR Corp., is a parent holding company in accordance  
with Section 240.13d-1(b)(ii)(G).  (Note:  See Item 7).  
  
Item 4.	Ownership  
  
	(a)	Amount Beneficially Owned: 
	2,667,400  
  
	(b)	Percent of Class: 
	11.089%  
  
	(c)	Number of shares as to which such person has:    
  
	(i)	sole power to vote or to direct the vote: 
	120,400  
  
	(ii)	shared power to vote or to direct the vote: 
	0  
  
	(iii)	sole power to dispose or to direct the disposition of: 
	2,667,400  
  
	(iv)	shared power to dispose or to direct the disposition of: 
	0  
  
  
 
 
Item 5.	Ownership of Five Percent or Less of a Class.  
  
	Not applicable.  
  
Item 6.	Ownership of More than Five Percent on Behalf of Another Person.  
  
	Various persons have the right to receive or the power to  
direct the receipt of dividends from, or the proceeds from the  
sale of, the Common Stock of Premisys Communications  
Incorporated.  No one person's interest in the Common Stock of  
Premisys Communications Incorporated is more than five percent  
of the total outstanding Common Stock.  
  
Item 7.	Identification and Classification of the Subsidiary Which Acquired  
the Security Being Reported on By the Parent Holding Company.  
  
	See attached Exhibit(s) A and B.  
  
Item 8.	Identification and Classification of Members of the Group.  
  
	Not applicable, see attached Exhibit A.   
  
Item 9.	Notice of Dissolution of Group.  
  
	Not applicable.  
  
Item 10.	Certification.  
  
	By signing below I certify that, to the best of my knowledge  
and belief, the securities referred to above were acquired in  
the ordinary course of business and were not acquired for the  
purpose of and do not have the effect of changing or  
influencing the control of the issuer of such securities and  
were not acquired in connection with or as a participant in any  
transaction having such purpose or effect.  
  
  
Signature  
  
	After reasonable inquiry and to the best of my knowledge and  
belief, I certify that the information set forth in this  
Schedule 13G in connection with FMR Corp.'s beneficial  
ownership of the Common Stock of Premisys Communications  
Incorporated at December 31, 1998 is true, complete and  
correct.   
  
  
	January 7, 1999	  
Date  
  
  
  
	/s/Eric D. Roiter  
Signature  
  
  
  
	Eric D. Roiter	  
Duly authorized under Power of  
Attorney  
dated December 30, 1997, by  
and on behalf  
of FMR Corp. and its direct  
and indirect  
subsidiaries  
  
  
 
 
SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS  
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)  
  
	Pursuant to the instructions in Item 7 of Schedule 13G, Fidelity  
Management & Research Company ("Fidelity"), 82 Devonshire Street, Boston,  
Massachusetts 02109, a wholly-owned subsidiary of FMR Corp. and an investment  
adviser registered under Section 203 of the Investment Advisers Act of 1940,  
is the beneficial owner of 2,547,000 shares or 10.589% of the Common Stock  
outstanding of Premisys Communications Incorporated ("the Company") as a  
result of acting as investment adviser to various investment companies  
registered under Section 8 of the Investment Company Act of 1940.    
  
	Edward C. Johnson 3d, FMR Corp., through its control of Fidelity, and the  
funds each has sole power to dispose of the 2,547,000 shares owned by the  
Funds.  
  
	Neither FMR Corp. nor Edward C. Johnson 3d, Chairman of FMR Corp., has  
the sole power to vote or direct the voting of the shares owned directly by  
the Fidelity Funds, which power resides with the Funds' Boards of Trustees.   
Fidelity carries out the voting of the shares under written guidelines  
established by the Funds' Boards of Trustees.  
  
	Fidelity Management Trust Company, 82 Devonshire Street, Boston,  
Massachusetts 02109, a wholly-owned subsidiary of FMR Corp. and a bank as  
defined in Section 3(a)(6) of the Securities Exchange Act of 1934, is the  
beneficial owner of 120,400 shares or 0.500% of the Common Stock outstanding  
of the Company as a result of its serving as investment manager of the  
institutional account(s).    
  
	Edward C. Johnson 3d and FMR Corp., through its control of Fidelity  
Management Trust Company, each has sole voting and dispositive power over  
120,400 shares of Common Stock owned by the institutional account(s) as  
reported above.  
  
	Members of the Edward C. Johnson 3d family and trusts for their benefit  
are the predominant owners of Class B shares of common stock of FMR Corp.,  
representing approximately 49% of the voting power of FMR Corp.  Mr. Johnson  
3d owns 12.0% and Abigail Johnson owns 24.5% of the aggregate outstanding  
voting stock of FMR Corp.  Mr. Johnson 3d is Chairman of FMR Corp. and Abigail  
P. Johnson is a Director of FMR Corp.  The Johnson family group and all other  
Class B shareholders have entered into a shareholders' voting agreement under  
which all Class B shares will be voted in accordance with the majority vote of  
Class B shares.  Accordingly, through their ownership of voting common stock  
and the execution of the shareholders' voting agreement, members of the  
Johnson family may be deemed, under the Investment Company Act of 1940, to  
form a controlling group with respect to FMR Corp.    
 
 
SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS  
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)  
RULE 13d-1(f)(1)  AGREEMENT  
  
	The undersigned persons, on January 7, 1999, agree and consent to the  
joint filing on their behalf of this Schedule 13G in connection with their  
beneficial ownership of the Common Stock of Premisys Communications  
Incorporated at December 31, 1998.  
	FMR Corp.  
	By	/s/Eric D. Roiter  
Eric D. Roiter 
Duly authorized under of Power  
of Attorney  
dated December 30, 1997, by  
and on behalf  
of FMR Corp. and its direct  
and indirect subsidiaries  
	Edward C. Johnson 3d  
	By	/s/Eric D. Roiter  
Eric D. Roiter 
Duly authorized under Power of  
Attorney  
dated December 30, 1997, by  
and on behalf  
of Edward C. Johnson 3d  
	Abigail P. Johnson  
	By	/s/Eric D. Roiter  
Eric D. Roiter 
Duly authorized under Power of  
Attorney  
dated December 30, 1997, by  
and on behalf  
of Abigail P. Johnson  
	Fidelity Management & Research Company  
	By	/s/Eric D. Roiter  
Eric D. Roiter 
V.P. and General Counsel