Clocks (including RTC)

TN0108

20/26

Doc ID 15874 Rev 2

7

Clocks (including RTC)

7.1

Invalid clock selection inhibit

On Cut 1.1 devices, whenever an attempt was made to access a peripheral that had the

peripheral clock disabled, the system hung with no response.

On Cut 2 devices, this has been fixed such that the system no longer hangs. If the RAE bit is

set within the SSCM_ERROR register, then the user will be notified of an access problem

with an IVOR2 exception. The clock status of each peripheral (enabled or disabled) can be

determined by reading the ME_PSx registers.

7.2

RTC counter updates

On Cut 1.1 devices, the RTC has to be halted (by writing to the CNTEN bit in the RTC

Control register) before the RTC compare value (RTCVAL) is changed. This not only

stopped the counter, but also had the effect of resetting the counter.

A modification has been made on Cut 2 devices, so that the RTCVAL can be changed

without halting the counter.

Note:

For customers who have written code to change the counter value in Cut 1.1, you need to

be careful of the fact that the counter is reset when CNTEN is cleared. On Cut 2 you may

get a timer compare almost immediately after modifying the RTVAL.

Table 19.

Unclocked peripheral behavior

Silicon revision

Behavior on accessing unclocked peripheral

SPC560B Cut 1.1

Non-recoverable system hang.

SPC560B Cut 2

System does not hang. User notified via IVOR2 exception.

Table 20.

Real-time counter

Silicon revision

Change RTCVAL

Comments

SPC560B Cut 1.1

Halt Counter, then change RTVAL

Counter is reset when CNTEN is

cleared

SPC560B Cut 2

Change RTVAL when counter is running

No need to stop counter