Unknown Year, 5.2L MC68HC16Z2 Initialization Code Overview

• Reset Vector = 0x0

First byte of reset vector = PK (Program Counter Extension)

Second byte of reset vector = SK (Stack Pointer Extension)

Third byte of reset vector = ZK (Index Z Extension)

PK = 0x01

SK = 0xFF

ZK = 0xFF

Initial PC = 0x0 | PK = (0x10000)

• 0x10000 Jump to 0x20000

• 0x20002 Wrote 0xFF to SK

• 0x20004 Wrote 0xFF to ZK

• 0x20006 Wrote 0xF8FE to SP

• 0x2000A Wrote 0xF800 to Z

• 0x20010 Wrote 0x00 to EK, XK, & YK

• 0x2001E Write 0xB4 to SYPCR

Enabled Watchdog

Turned off scaling

Set timeout to 2 to the 15th

• 0x20024 Wrote 0x55 to SWSR

• 0x2002A Wrote 0xAA to SWSR

Writing 0x55 then 0xAA to SWSR pets the watchdog

• 0x20032 Wrote 0xFF to RAMBAH
• 0x2003A Wrote 0x8000 to RAMBAL

This set RAM to start at 0xF8000

• 0x2003E cleared RAMMCR

Took RAM out of low power mode and enabled it.

Allowed writes to RAM from IMB

• 0x2004C ORed 0x8100 to SIMCR

Turned off external clock

Set external bus master to have direct access to IMB

• 0x20052 Wrote 0x30 to PEPAR

Port E Pin Assignment

Set PEPA5 as Address Strobe

Set PEPA4 as Data Strobe

• 0x20056 Wrote 0x30 to DDRE

Port E Pin Direction

Set DDE5 & DDE4 as outputs