GOODWILL AND INTANGIBLE ASSETS (Net intangible assets) (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 28, 2020	Sep. 28, 2019
Finite-Lived Intangible Assets [Line Items]
Net intangible assets	$ 39,757	$ 42,651
Developed technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets	88,184	87,209
Accumulated amortization	(51,124)	(48,718)
Net intangible assets	37,060	38,491
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets	35,466	35,180
Accumulated amortization	(33,435)	(31,862)
Net intangible assets	2,031	3,318
Trade name [Member]
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets	7,265	7,219
Accumulated amortization	(6,599)	(6,377)
Net intangible assets	666	842
Other intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets	2,500	2,500
Accumulated amortization	(2,500)	(2,500)
Net intangible assets	$ 0	$ 0
Average estimated useful lives (in years)	1 year 10 months 24 days
Minimum | Developed technology [Member]
Finite-Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	7 years
Minimum | Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	5 years
Minimum | Trade name [Member]
Finite-Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	7 years
Maximum | Developed technology [Member]
Finite-Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	15 years
Maximum | Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	6 years
Maximum | Trade name [Member]
Finite-Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	8 years