Clock Control

The configuration of bits in the clock speed control register appears below:

ClkSpdCtrl register

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

address 0x3D

(16-bit wide location)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

WRITE only

15

14

13

12

11

10

09 08

07

06

05

04

03

02

01

00

 

T5

T4

T3

T2

T1

 

I

C or T0 R

 

M

M

M

M

M

M

M

M

T : RTO oscillator-Trim adjust

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R

: enable Resistor-trimmed oscillator

 

 

 

I : Idle State clock Control

 

 

 

 

 

 

M : PLLM multiplier bits for MC

 

 

 

 

C : enable Crystal oscillator

 

 

 

 

 

 

0x0000 : default state after RESET LOW

 

 

 

(or T0 if R is set

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bit 10 in the ClkSpdCtrl is idle state clock control. The level of deep-sleep generated by the IDLE instruction is partially controlled by this bit. When this bit is cleared (default setting), the CPU clock is stopped during the sleep, but the MC remains running. When the idle state clock control bit is set, both the CPU clock and the MC are stopped during sleep. Refer to section 2.11 for more information regarding the C6xx’s reduced-power modes.

Note: Reference Oscillator Stopped by Programmed Disable

If the reference oscillator is stopped by a programmed disable, then, on re- enable, the oscillator requires some time to restart and resume its correct fre- quency. This time imposes a delay on the core processor resuming full- speed operation. The time-delay required for the CRO to start is GREATER than the time-delay required for the RTO to start.

2.8.4RTO Oscillator Trim Adjustment

Bits 15 through 11 and bit 9 (6 bits total) in the ClkSpdCtrl effect a software control for the RTO oscillator frequency. The purpose of this control is to trim the RTO to its rated (32 kHz) specification. The correct trim value varies from device to device. The user must program bits 15 through 11 and 9, in order to achieve the 32-kHz specification within the rated tolerances. Texas Instruments provides the trim value to the programmer of the P614 part with a sticker on the body of the chip. For the C6xx parts, the correct trim value is located at I/O location 0x2Fh.

MSP50C6xx Architecture

2-29

Page 53
Image 53
Texas Instruments MSP50C6xx manual RTO Oscillator Trim Adjustment, ClkSpdCtrl register