Memory Map and Registers

 

 

Table 18-4. WMR Field Descriptions

 

 

 

 

Bit(s)

Name

Description

 

 

 

 

 

15–0

WM

Watchdog modulus. Contains the modulus that is reloaded into the watchdog counter by a

 

 

 

service sequence. Once written, the WM[15:0] field is not affected by further writes except in

 

 

 

halted mode. Writing to WMR immediately loads the new modulus value into the watchdog

 

 

 

counter. The new value is also used at the next and all subsequent reloads. Reading WMR

 

 

 

returns the value in the modulus register.

 

 

 

Reset initializes the WM[15:0] field to 0xFFFF.

 

 

 

Note: The prescaler counter is reset anytime a new value is loaded into the watchdog counter

 

 

 

and also during reset.

 

 

 

 

 

18.5.2.3Watchdog Count Register (WCNTR)

 

 

15

14

13

12

 

11

 

10

9

8

 

Field

WC15

 

 

WC14

WC13

WC12

 

WC11

 

WC10

WC9

WC8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reset

 

 

 

 

 

1111_1111

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R/W

 

 

 

 

 

R

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

7

6

5

4

 

3

 

2

1

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Field

WC7

 

 

WC6

WC5

WC4

 

WC3

 

WC2

WC1

WC0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reset

 

 

 

 

 

1111_1111

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R/W

 

 

 

 

 

R

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Address

 

 

 

 

IPSBAR + x0014_0004, 0x0014_0005

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 18-4. Watchdog Count Register (WCNTR)

 

 

 

 

 

 

 

 

Table 18-5. WCNTR Field Descriptions

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bit(s)

 

Name

 

 

 

 

 

Description

 

 

 

 

 

 

 

 

 

 

15–0

 

WC

 

 

Watchdog count field. Reflects the current value in the watchdog counter. Reading the 16-bit

 

 

 

 

 

WCNTR with two 8-bit reads is not guaranteed to return a coherent value. Writing to WCNTR

 

 

 

 

 

has no effect, and write cycles are terminated normally.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

18.5.2.4Watchdog Service Register (WSR)

When the watchdog timer is enabled, writing 0x5555 and then 0xAAAA to WSR before the watchdog counter times out prevents a reset. If WSR is not serviced before the timeout, the watchdog timer sends a signal to the reset controller module that sets the RSR[WDR] bit and asserts a system reset.

Both writes must occur in the order listed before the timeout, but any number of instructions can be executed between the two writes. However, writing any value other than 0x5555 or 0xAAAA to WSR resets the servicing sequence, requiring both values to be written to keep the watchdog timer from causing a reset.

MOTOROLA

Chapter 18. Watchdog Timer Module

18-5

Page 413
Image 413
Motorola MCF5281, MCF5282 Watchdog Count Register Wcntr, Watchdog Service Register WSR, WMR Field Descriptions, WC9 WC8