DEMO9S08EL32 Freescale Semiconductor, DEMO9S08EL32 Datasheet - Page 275

• Manufacturer Part Number: DEMO9S08EL32
• Description: BOARD DEMO FOR 9S08 EL MCU
• Manufacturer: Freescale Semiconductor
• Type: MCUr

Specifications of DEMO9S08EL32

• Contents: Evaluation Board
• Processor To Be Evaluated: MC9S08EL32
• Data Bus Width: 8 bit
• Interface Type: RS-232, USB
• Operating Supply Voltage: 12 V
• Silicon Manufacturer: Freescale
• Core Architecture: HCS08
• Core Sub-architecture: HCS08
• Silicon Core Number: MC9S08
• Silicon Family Name: S08EL
• Rohs Compliant: Yes
• For Use With/related Products: MC9S08EL32
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Real-Time Counter (S08RTCV1)
Internal 1-kHz
Clock Source
RTC Clock
(RTCPS = 0xA)
RTCCNT
0x52
0x53
0x54
0x55
0x00
0x01
RTIF
RTCMOD
0x55
Figure 15-6. RTC Counter Overflow Example
In the example of
Figure
15-6, the selected clock source is the 1-kHz internal oscillator clock source. The
prescaler (RTCPS) is set to 0xA or divide-by-4. The modulo value in the RTCMOD register is set to 0x55.
When the counter, RTCCNT, reaches the modulo value of 0x55, the counter overflows to 0x00 and
continues counting. The real-time interrupt flag, RTIF, sets when the counter value changes from 0x55 to
0x00. A real-time interrupt is generated when RTIF is set, if RTIE is set.
15.5
Initialization/Application Information
This section provides example code to give some basic direction to a user on how to initialize and
configure the RTC module. The example software is implemented in C language.
The example below shows how to implement time of day with the RTC using the 1-kHz clock source to
achieve the lowest possible power consumption. Because the 1-kHz clock source is not as accurate as a
crystal, software can be added for any adjustments. For accuracy without adjustments at the expense of
additional power consumption, the external clock (ERCLK) or the internal clock (IRCLK) can be selected
with appropriate prescaler and modulo values.
/* Initialize the elapsed time counters */
Seconds = 0;
Minutes = 0;
Hours = 0;
Days=0;
/* Configure RTC to interrupt every 1 second from 1-kHz clock source */
RTCMOD.byte = 0x00;
RTCSC.byte = 0x1F;
/**********************************************************************
Function Name : RTC_ISR
Notes : Interrupt service routine for RTC module.
**********************************************************************/
MC9S08EL32 Series and MC9S08SL16 Series Data Sheet, Rev. 3
Freescale Semiconductor
277