ECSM's software watchdog timer is not recommended to use on MPC5554 device.
For core watchdog you may see following appnote:
https://www.nxp.com/docs/en/application-note/AN2817.pdf
If you want only disable core watchdog, you may use following function:
asm
{
mfhid0 r11 /* Move from spr HID0 to r11 (copies HID0) */
li r12, 0xBFFF /* Load immed. data of ~0x4000 to r12 */
oris r12, r12, 0xFFFF
and r11, r12, r11 /* OR r12 (~0x00004000) with r11 (HID0 value) */
mthid0 r11 /* Move result to HID0 */
lis r12, 0x00
mtspr tcr, r12 /* clear SPR TCR register */
}
