4.3.4. Oscillator registers, SYS_OSCx

The oscillator registers, SYS_OSC0 to SYS_OSC4, at 0x1000000C-0x1000001C are read/write registers that control the frequency of the clocks generated by the ICS307 programmable oscillators. A serial interface transfers the values in the registers to the programmable oscillators when a reset occurs.

Figure 4.5 shows the bit assignment of the registers.

Figure 4.5. Oscillator Register, SYS_OSCx

Oscillator Register, SYS_OSCx

Table 4.7 lists the details of the SYS_OSCx registers. For more detail on bit values, see ICS307 programmable clock generators and Clock frequency restrictions.

Table 4.7. Oscillator Register, SYS_OSCx bit assignment

Bits

Access

Description

[31:19]

Reserved, Use read-modify-write to preserve value.

[18:16]

Read/Write

DIVIDE[2:0], output divider select

[15:9]

Read/Write

RDW[6:0], reference divider word

[8:0]

Read/Write

VDW[8:0], VCO divider word

Note

Before writing to a SYS_OSC register, unlock it by writing the value 0x0000A05F to the SYS_LOCK register. After writing the SYS_OSC register, relock it by writing any value other than 0x0000A05F to the SYS_LOCK register.

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