Appendix B: System Development Example MTT48 V2.1 B - 1 APPENDIX B: SYSTEM DEVELOPMENT

Appendix B: System Development Example MTT48 V2.1 B HC08 SYSTEM EXAMPLE Simple application set-up Power-On / Reset CPU Initialization Memory initialization

Appendix B: System Development Example MTT48 V2.1 B - 4 APPLICATION DESCRIPTION Basic automotive instrument cluster panel Displays PRNDL setting based on 3 discrete inputs –Port A PTA2-PTA0 Calculates and displays vehicle speed by measuring a pulse frequency –1 Pulse indicates 1 revolution of wheel axle –Input on timer channel 1 Receives data relating to warning lamps from powertrain control module via SCI at 9600 baud –Eight warning lamp discrete outputs on Port B (Engine over-temp, low oil pressure, low fuel, service engine, etc.)

Appendix B: System Development Example MTT48 V2.1 B - 5 APPLICATION DESCRIPTION (CONT.) Receives battery voltage, coolant temperature, and outside air temperature values from 8 bit A/D converter via SPI –Port A Bit 7 as SS line for A/D Key in ignition generates an external Interrupt on IRQ2 4 MHz external crystal and desire 8 MHz bus frequency

Appendix B: System Development Example MTT48 V2.1 B - 6 INSTRUMENT PANEL CONTROLLER IRQ2 Key in ignition PTB0 PTB1 PTB2 PTB3 PTB4 PTB5 PTB6 PTB7 Warning Light 1 Warning Light 2 Warning Light 3 Warning Light 5 Warning Light 6 Warning Light 7 Warning Light 8 Warning Light 4 68HC708XL36 8-Bit A/D SS PTA7 SPSCK MOSI MISO SPSCK MOSI MISO Battery Voltage Coolant Temp Air Temperature (SCI) TXD (SCI) RXD To Powertrain Control Module From Powertrain Control Module PTA2 PTA1 PTA0 From PRNDL Switch 3 From PRNDL Switch 2 From PRNDL Switch 1 TCH1 Axle Ref. Pulses

Appendix B: System Development Example MTT48 V2.1 B - 7 POWER-ON RESET At Reset, the following occurs All registers set to initial default values Interrupts are disabled Stack Pointer set to $00FF Program Counter load with value at $FFFE-$FFFF Program execution begins

Appendix B: System Development Example MTT48 V2.1 B - 8 CPU INITIALIZATION Set proper bus frequency of 8 MHz Configure CGM for proper bus frequency –Must use PLL, N = 8, L = 6 –See CGM exercise May wish to move stack location Example: Move stack to address $0100 LDHX #$0101 TXS; Subtracts 1 in process Initialize/clear RAM to known state Could be performed using DMA –See DMA exercise part 4

Appendix B: System Development Example MTT48 V2.1 B - 9 CPU INITIALIZATION If using interrupts Initialize interrupt service routines –TIM Channel 1 –SCI Transmit and Receive –SPI Transmit and Receive –IRQ2 Enable interrupts

Appendix B: System Development Example MTT48 V2.1 B - 10 I/O PORT INITIALIZATION NOTE:Order of submodule initialization may or may not be critical to application Configure I/O Ports PRNDL –Set Port A Data Direction Bits 2-0 as inputs (default) A/D Slave Select Line –Set Port A Data Bit 7 to 1 to disable SS line –Set Port A Data Direction Bit 7 as an output Warning lamps –Write $00 to Port B Data register to deactivate warning lamps –Set all Port B Data Direction bits to outputs

Appendix B: System Development Example MTT48 V2.1 B - 11 SPI MODULE INITIALIZATION Configure SPI module Select Master mode, polarity, phase and baud rate –SPMSTR bit = 1 –CPOL,CPHA = 01 Idle low, Read data on 2nd clock edge –SPR1:SPR0 = 10 Baud rate of 250 KHz (8 MHz bus) Turn on SPI –Set SPE bit in SPI Control register Interrupts –Enable interrupts as required by application SPIE bit for transmission complete interrupt (SPIF) TDIE bit for transmit register empty interrupt (TDRE)

Appendix B: System Development Example MTT48 V2.1 B - 12 SCI MODULE INITIALIZATION Configure SCI module to communicate with Powertrain Control Module Select number of data bits, parity, and baud rate –M = 0 8 data bits –PEN,PTY = 0X Parity disabled, Parity Type is don’t care –SCP1:SCP0 = 01 Prescaling of 3 –SCR2:SCR1:SCR0 = 001 Divisor of 2 ­ 9600 baud from 4 MHz external crystal frequency Turn on SCI –Set ENSCI bit in SCI Control Register 1 Interrupts –Enable interrupts as required by application TCIE bit for transmission complete interrupt (TC) TIE bit for transmit register empty interrupt (TDRE) RIE bit for data received interrupt (RDRF) Error interrupts (OR, NF, FE, PE)

Appendix B: System Development Example MTT48 V2.1 B - 13 TIM INITIALIZATION Initialize TIM module for measuring wheel speed reference pulse frequency Configure prescaler value smallest resolution –PS2:PS1:PS0 = 000 System clock ÷ 1 (default) Resolution = 125 ns at 8 MHz bus clock Configure channel 1 for input capture on rising edge –MS1A = 0Input capture –ELS1B:ELS1A = 01 Rising edge detection Interrupt as needed by application –Set CH1E bit for interrupt generation on capture Enable Timer –Clear TSTOP bit in Timer Control Register

Appendix B: System Development Example MTT48 V2.1 B - 14 ADDITIONAL INITIALIZATION Initialize any RAM locations as required by application Begin Program execution

Appendix B: System Development Example MTT48 V2.1 B - 15 OPTIONAL INITIALIZATION Configure DMA module as needed by application Could use DMA to service SCI or SPI interrupts Set channel source and destination register addresses Set-up register Set-up Source/Destination address calculation –Interrupt source –Byte/Word Count Enable channel in DMA Control Register 1 (DC1) –Set Channel enable bit Interrupt on complete of transfer –Set Channel interrupt enable bit in DC1

Appendix B: System Development Example MTT48 V2.1 B - 16 OPTIONAL INITIALIZATION Enable COP module Clear COPD bit MOR register –Must be done at EPROM programming time Enable LVI module Set LVIPWR bit in LVI Status and Control register Enable Reset Generation if desired –Set LVIRST bit Lock LVI –Set LVILCK bit to write protect register –Think low power modes

Appendix B: System Development Example MTT48 V2.1 B - 17 ADDITIONAL SYSTEM CONFIGURATION Before executing WAIT or STOP configure XIRQ module Enable IRQ2 interrupt Clear IMASK2 in IRQ Status and Control register

Appendix B: System Development Example MTT48 V2.1 B - 18 SYSTEM CONFIGURATION EXAMPLE Questions and Answers