Real Time Clock

The Real Time Clock has previously been handled by the Kernel. With Kernel 8.64 and later the clock is managed by the RTC module. This communicates with the hardware driver through a vector (RTCV), whose default claimant is the RTCHW module. The RTCHW module provides implementations for the RiscPC, A7000-series, RiscStation, and A9.

The RTC module provides the Kernel SWI OS_ResyncTime, and all the OS_Word 14 and 15 operations to control the clock. A new reason code has been added to OS_Word 15 for setting the clock's 5 byte time directly. See the OS_Word15 document for more details.

A separate document describes the RTCV vector.

OS_ResyncTime (&6C)
on entry

   R0 = reason code :
        0 = synchronise with hardware clock
   other  reserved

This SWI is used to cause the software clock to be resynchronised with the hardware clock, where available. When changed, a service call Service_RTCSynchronised will be issued. This call was new to RISC OS 4.

Service_RTCSynchronised (&DD)
on entry

   R1 = &DD

on exit

   R1 preserved to pass on (do not claim)

This service is issued by the RTC module to inform clients that the software and hardware clocks have been synchronised. It may indicate that an indeterminate period of inactivity has taken place, such as after returning from a suspend state. Where possible, timed events should be synchronised and where necessary appropriate action taken to ensure that queued events take place.

This service should never be claimed.

This documentation is copyright 3QD Developments Ltd 2013 and may not be reproduced or published in any form without the copyright holders permission. RISC OS is subject to continuous development and improvement as such all information is reproduced by 3QD Developments Ltd in good faith and is believed to be correct at the time of publication E&OE. 3QD Developments Ltd cannot accept any liability for any loss or damage arising from the use of any information provided as part of the RISC OS Documentation.

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