NXP Semiconductors MC9S08PA4, Reference Manual

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13.3.2 RTC Status and Control Register 2 (RTC_SC2)
RTC_SC2 contains the clock select bits (RTCLKS) and the prescaler select bits
(RTCPS).
Address: 306Ah base + 1h offset = 306Bh
Bit 7 6 5 4 3 2 1 0
Read
RTCLKS
0
RTCPS
Write
Reset 0 0 0 0 0 0 0 0
RTC_SC2 field descriptions
Field Description
7–6
RTCLKS
Real-Time Clock Source Select
These two read/write bits select the clock source input to the RTC prescaler. Changing the clock source
clears the prescaler and RTCCNT counters. Reset clears RTCLKS to 00.
00 External clock source.
01 Real-time clock source is 1 kHz.
10 Bus clock.
11 Bus clock.
5–3
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
RTCPS Real-Time Clock Prescaler Select
These four read/write bits select binary-based or decimal-based divide-by values for the clock source.
Changing the prescaler value clears the prescaler and RTCCNT counters. Reset clears RTCPS to 0000.
000 Off
001 If RTCLKS = x0, it is 1; if RTCLKS = x1, it is 128.
010 If RTCLKS = x0, it is 2; if RTCLKS = x1, it is 256.
011 If RTCLKS = x0, it is 4; if RTCLKS = x1, it is 512.
100 If RTCLKS = x0, it is 8; if RTCLKS = x1, it is 1024.
101 If RTCLKS = x0, it is 16; if RTCLKS = x1, it is 2048.
110 If RTCLKS = x0, it is 32; if RTCLKS = x1, it is 100.
111 If RTCLKS = x0, it is 64; if RTCLKS = x1, it is 1000.
Register definition
MC9S08PA4 Reference Manual, Rev. 5, 08/2017
262 NXP Semiconductors