PMC153 datasheet(21/57 Pages) PADAUK

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PMC153/PMS153 Series

8-bit OTP Type IO Controller

Page 21 of 57

PDK-DS-PMX153-EN_V108 –Dec. 26, 2019

5.3. Data Memory – SRAM

The access of data memory can be byte or bit operation. Besides data storage, the SRAM data memory is

also served as data pointer of indirect access method and the stack memory.

The stack memory is defined in the data memory. The stack pointer is defined in the stack pointer register; the

depth of stack memory of each processing unit is defined by the user. The arrangement of stack memory fully

flexible and can be dynamically adjusted by the user.

For indirect memory access mechanism, the data memory is used as the data pointer to address the data

byte. All the data memory could be the data pointer; it’s quite flexible and useful to do the indirect memory

access. All the 64 bytes data memory of PMC153/PMS153 can be accessed by indirect access mechanism.

5.4. Oscillator and clock

There are two oscillator circuits provided by PMC153/PMS153: internal high RC oscillator (IHRC) and internal

low RC oscillator (ILRC), and these two oscillators are enabled or disabled by registers clkmd.4 and clkmd.2

independently. User can choose one of these two oscillators as system clock source and use clkmd register

to target the desired frequency as system clock to meet different application.

Oscillator Module

Enable/Disable

IHRC

clkmd.4

ILRC

clkmd.2

Table2: Two Oscillators provided by PMC153/PMS153

5.4.1 Internal High RC oscillator and Internal Low RC oscillator

After boot-up, the IHRC and ILRC oscillators are enabled. The frequency of IHRC can be calibrated to

eliminate process variation by ihrcr register; normally it is calibrated to 16MHz. The frequency deviation can

be within 2% normally after calibration and it still drifts slightly with supply voltage and operating temperature.

Please refer to the measurement chart for IHRC frequency VS VDD and IHRC frequency VS temperature.

The frequency of ILRC will vary by process, supply voltage and temperature, please refer to DC specification

and do not use for accurate timing application.

5.4.2 IHRC calibration

The IHRC frequency may be different chip by chip due to manufacturing variation, PMC153/PMS153 provide

the IHRC frequency calibration to eliminate this variation, and this function can be selected when compiling

user’s program and the command will be inserted into user’s program automatically. The calibration

command is shown as below:

.ADJUST_IC SYSCLK=IHRC/(p1), IHRC=(p2)MHz, VDD=(p3)V

Where,

p1=2, 4, 8, 16, 32; In order to provide different system clock.

p2=14 ~ 18; In order to calibrate the chip to different frequency, 16MHz is the usually one.

p3=2.2 ~ 5.5; In order to calibrate the chip under different supply voltage.

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