Product data

Product data sheet Rev. 2 — 18 April 2014 11 of 60

NXP Semiconductors

UJA1167

Mini high-speed CAN system basis chip with Standby/Sleep modes &

watchdog

6.2 Watchdog

The UJA1167 contains a watchdog that supports three operating modes: Window,

Timeout and Autonomous. In Window mode (available only in SBC Normal mode), a

watchdog trigger event within a closed watchdog window resets the watchdog timer. In

Timeout mode, the watchdog runs continuously and can be reset at any time within the

timeout time by a watchdog trigger. Watchdog timeout mode can also be used for cyclic

wake-up of the microcontroller. In Autonomous mode, the watchdog can be off or in

Timeout mode (see Section 6.2.4

The watchdog mode is selected via bits WMC in the Watchdog control register (Table 7

The SBC must be in Standby mode when the watchdog mode is changed. If Window

mode is selected (WMC = 100), the watchdog will remain in (or switch to) Timeout mode

until the SBC enters Normal mode. Any attempt to change the watchdog operating mode

(via WMC) while the SBC is in Normal mode will cause the UJA1167 to switch to Reset

mode and the reset source status bits (RSS) will be set to 10000 (‘illegal watchdog mode

control access’; see Table 5

Eight watchdog periods are supported, from 8 ms to 4096 ms. The watchdog period is

programmed via bits NWP. The selected period is valid for both Window and Timeout

modes. The default watchdog period is 128 ms.

Table 5. Main status register (address 03h)

Bit Symbol Access Value Description

7 reserved R -

6 OTWS R overtemperature warning status:

0 IC temperature below overtemperature warning threshold

1 IC temperature above overtemperature warning threshold

5 NMS R Normal mode status:

0 UJA1167 has entered Normal mode (after power-up)

1 UJA1167 has powered up but has not yet switched to

Normal mode

4:0 RSS R reset source status:

00000 exited Off mode (power-on)

00001 CAN wake-up in Sleep mode

00100 wake-up via WAKE pin in Sleep mode

01100 watchdog overflow in Sleep mode (Timeout mode)

01101 diagnostic wake-up in Sleep mode

01110 watchdog triggered too early (Window mode)

01111 watchdog overflow (Window mode or Timeout mode with

WDF = 1)

10000 illegal watchdog mode control access

10001 RSTN pulled down externally

10010 exited Overtemp mode

10011 V1 undervoltage

10100 illegal Sleep mode command received