GOODWILL AND INTANGIBLE ASSETS (Net intangible assets) (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 27, 2020	Sep. 28, 2019
Finite-Lived Intangible Assets [Line Items]
Net intangible assets	$ 38,207	$ 42,651
Developed technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets	88,591	87,209
Accumulated amortization	(52,327)	(48,718)
Net intangible assets	36,264	38,491
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets	35,586	35,180
Accumulated amortization	(34,218)	(31,862)
Net intangible assets	1,368	3,318
Trade name [Member]
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets	7,285	7,219
Accumulated amortization	(6,710)	(6,377)
Net intangible assets	575	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