Designing a USB Keyboard and PS/2® Mouse Combination Device ...

Designing a USB Keyboard and PS/2 Combination DeviceConclusionThe two main enabling factors of the proliferation of the USBdevices are cost and functionality. The CY7C63413 meetsboth requirements by integrating the USB SIE and multi-functionI/Os with a USB optimized RISC core in a low-cost part.In this application note, the CY7C63413 USB microcontrolleris used to implement a USB keyboard and PS/2 mouse combinationdevice. The PS/2 interface, fully implemented in firmware,preserves the use of a legacy PS/2 mouse without anyadditional cost.1 ms ISRClear Watchdog Timer3 ms ofbus inactivity?NoYesSave GPIO PortSettingsWrite ‘0’ to KeyboardColumn Port BitsEnable GPIO Interrupton Port 2 and 3Set the PS/2 Mouseto Stream ModeGo SuspendRESUMERestore GPIO PortSettingsDisable GPIO Interrupton Port 2Has 12 mspast?YesKeyboard DebounceFIFO incrementNoRestore PS/2 Mouseto Remote ModePS/2 MouseTimeout CheckReturnFigure 11. 1 ms Interrupt Service RoutinePS/2 is a registered trademark of the International Business Machines Corp.© Cypress Semiconductor Corporation, 1998. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the useof any circuitry other than circuitry embodied in a Cypress Semiconductor product. Nor does it convey or imply any license under patent or other rights. Cypress Semiconductor does not authorizeits products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of CypressSemiconductor products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress Semiconductor against all charges.