Microsoft has sued Motorola over patent fees for Xbox 360 technology licensed from the phone maker.
According to MS, Motorola has breached contractual obligations to fairly license patents on wireless networking and video coding featured in its games console.
"Motorola has refused to extend to Microsoft a license consistent with Motorola's promises for any of Motorola's identified patents," MS said in its complaint, according to Bloomberg.
"Instead, Motorola is demanding royalty payments that are wholly disproportionate to the royalty rate that its patents should command under any reasonable calculus."
Unsurprisingly, Motorola tells a different story.
"We worked with Microsoft to reach an agreement that would have allowed Microsoft to use our proprietary technologies without infringing Motorola's patents," said company spokesperson Jennifer Erickson.
"Unfortunately, despite a fair offer from Motorola, Microsoft was unwilling to enter into a licensing agreement."
Three weeks ago Microsoft also filed patent-infringement claims against Motorola in a bid to block US imports of the firm's Android phones.