MC9S08GT16A Datasheet, PDF (125/300 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 9
Internal Clock Generator (S08ICGV4)
9.1 Introduction
The MC9S08GT16A/GT8A microcontroller provides one internal clock generation (ICG) module to
create the system bus frequency. All functions described in this section are available on the
MC9S08GT16A/GT8A microcontroller. The EXTAL and XTAL pins share port G bits 2 and 1,
respectively. Analog supply lines V_DDA and V_SSA are internally derived from the MCU’s V_DD and V_SS
pins. Electrical parametric data for the ICG may be found in Appendix A, “Electrical Characteristics.”
SYSTEM
CONTROL
LOGIC
ICGERCLK
RTI
FFE
TPM1
TPM2
IIC1
SCI1
SCI2
SPI1
÷2
ICG
FIXED FREQ CLOCK (XCLK)
ICGOUT
÷2
ICGLCLK*
BUSCLK
CPU
BDC
COP
ATD1
RAM
FLASH
ATD has min and max
FLASH has frequency
frequency requirements. See
requirements for program
* ICGLCLK is the alternate BDC clock source for the MC9S08GT16A/GT8A. Chapter 14, “Analog-to-Digital Convert- and erase operation.
er (S08ATDV3),” and Appendix A, See Appendix A, “Electrical
“Electrical Characteristics.”
Characteristics.”
Figure 9-1. System Clock Distribution Diagram
NOTE
Freescale Semiconductor programs a factory trim value for ICGTRM into
the FLASH location $FFBE (NVICGTRM). Leaving this address for the
ICGTRM value also allows debugger and programmer vendors to perform
a manual trim operation and store the resultant ICGTRM value into
NVICGTRM for users to access at a later time. The value in NVICGTRM
is not automatically loaded and therefore must be copied into ICGTTRM by
user code.
MC9S08GT16A/GT8A Data Sheet, Rev. 1
Freescale Semiconductor
125