Clocks and Power Manager

3.6.3Oscillator Configuration Register (OSCC)

The OSCC, shown in Table 3-22, controls the 32.768 kHz oscillator configuration. It contains two bits, the set-only 32.768 KHz OSCC[OON] and the read-only 32.768 kHz OSCC[OOK]. OSCC[OON] enables the external 32.768 kHz oscillator and can only be set by software. When the oscillator is enabled, it takes up to 10 seconds for to stabilize. When the oscillator is stabilized, the processor sets OSCC[OOK].

When OSCC[OOK] is set, the RTC and PM are clocked from the 32.768 KHz oscillator. Otherwise, the 3.6864 MHz oscillator is used. The OPDE bit, which allows the 3.6864 MHz oscillator to be disabled in sleep mode, is ignored (treated as if it were clear) if OSCC[OOK] is clear. OSCC[OOK] can only be reset by a hardware reset.

This is a read/write register. Ignore reads from reserved bits. Write zeros to reserved bits.

Table 3-22. OSCC Bit Definitions

 

 

 

 

0x4130_0008

 

 

 

 

 

 

 

OSCC

 

 

 

 

 

 

Clocks and Power Manager

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bit

31 30 29 28 27

26

25 24 23

22 21 20

19

18 17 16 15

14 13 12

11

10

9

8

7

6

5

4

3

2

1

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

reserved

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OON

 

OOK

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reset

0

0

0

0

0

0

 

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bits

 

 

Name

 

 

 

 

 

 

 

 

 

 

 

Description

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[31:2]

 

 

 

 

reserved

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

32.768 KHz OON (write-once only bit)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0 – 32.768 KHz oscillator is disabled. The 3.6864 MHz oscillator (divided by 112) clocks

 

 

 

1

 

 

OON

 

 

the RTC and PM.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1 – 32.768 KHz oscillator is enabled. OON can not be cleared once written except by

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

hardware reset.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cleared by hardware reset.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

32.768 kHz OOK (read-only bit)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0 – 32.768 KHz oscillator is disabled or not stable. The 3.6864 MHz oscillator (divided

 

 

 

0

 

 

OOK

 

 

by 112) clocks the RTC and PM.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1 – 32.768 KHz oscillator has been enabled (OON=1) and stabilized. It will clock the

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RTC and PM.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cleared by hardware reset.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.7Coprocessor 14: Clock and Power Management

Coprocessor 14 contains two registers that control the power modes and sequences:

CP14 register 6 – CCLKCFG register

CP14 register 7 – PWRMODE register

3-38

Intel® PXA255 Processor Developer’s Manual

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Intel PXA255 manual Coprocessor 14 Clock and Power Management, Oscillator Configuration Register Oscc, Oscc Bit Definitions