SPRUJD3A July 2025 – October 2025 F28E120SB , F28E120SC
Table 3-53 lists the memory-mapped registers for the WD_REGS registers. All register offset addresses not listed in Table 3-53 should be considered as reserved locations and the register contents should not be modified.
| Offset | Acronym | Register Name | Write Protection |
|---|---|---|---|
| 22h | SCSR | System Control & Status Register | EALLOW |
| 23h | WDCNTR | Watchdog Counter Register | EALLOW |
| 25h | WDKEY | Watchdog Reset Key Register | EALLOW |
| 29h | WDCR | Watchdog Control Register | EALLOW |
| 2Ah | WDWCR | Watchdog Windowed Control Register | EALLOW |
Complex bit access types are encoded to fit into small table cells. Table 3-54 shows the codes that are used for access types in this section.
| Access Type | Code | Description |
|---|---|---|
| Read Type | ||
| R | R | Read |
| R-0 | R -0 | Read Returns 0s |
| Write Type | ||
| W | W | Write |
| W1S | W 1S | Write 1 to set |
| Reset or Default Value | ||
| -n | Value after reset or the default value | |
| Register Array Variables | ||
| i,j,k,l,m,n | When these variables are used in a register name, an offset, or an address, they refer to the value of a register array where the register is part of a group of repeating registers. The register groups form a hierarchical structure and the array is represented with a formula. | |
| y | When this variable is used in a register name, an offset, or an address it refers to the value of a register array. | |
SCSR is shown in Figure 3-47 and described in Table 3-55.
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System Control & Status Register
| 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 |
| RESERVED | |||||||
| R-0-0h | |||||||
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| RESERVED | WDINTS | WDENINT | WDOVERRIDE | ||||
| R-0-0h | R-1h | R/W-0h | R/W1S-1h | ||||
| Bit | Field | Type | Reset | Description |
|---|---|---|---|---|
| 15-3 | RESERVED | R-0 | 0h | Reserved |
| 2 | WDINTS | R | 1h | Watchdog Interrupt Status This bit indicates the state of the active-low watchdog interrupt signal (synchronized to SYSCLK). If the watchdog interrupt is used to wake the system from a low-power mode, then that mode should only be entered while this bit is high. Likewise, this bit must go high before the watchdog can be safely disabled and re-enabled. Reset type: SYSRSn |
| 1 | WDENINT | R/W | 0h | Watchdog Interrupt Enable/Reset Disable This bit determines whether the watchdog triggers an interrupt (WAKE/WDOG) or a reset (WDRS) when the counter expires. Reset type: SYSRSn |
| 0 | WDOVERRIDE | R/W1S | 1h | Watchdog Enable Lock Writing a 1 to this bit clears it and locks the WDDIS bit in the WDCR register. The bit will remain in this state until the next system reset. Reads of this bit return its current value. Writing a 0 to this bit has no effect. Reset type: SYSRSn |
WDCNTR is shown in Figure 3-48 and described in Table 3-56.
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Watchdog Counter Register
| 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 |
| RESERVED | |||||||
| R-0-0h | |||||||
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| WDCNTR | |||||||
| R-0h | |||||||
| Bit | Field | Type | Reset | Description |
|---|---|---|---|---|
| 15-8 | RESERVED | R-0 | 0h | Reserved |
| 7-0 | WDCNTR | R | 0h | Watchdog Counter These bits contain the current value of the watchdog counter. This counter increments with each WDCLK (scaled SECCLK) cycle. If the counter overflows, either an interrupt or a reset is generated based on the value of the WDINTEN bit in the SCSR register. If the correct value is written to the WDKEY register, this counter is reset to zero. Reset type: IORSn |
WDKEY is shown in Figure 3-49 and described in Table 3-57.
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Watchdog Reset Key Register
| 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 |
| RESERVED | |||||||
| R-0-0h | |||||||
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| WDKEY | |||||||
| R/W-0h | |||||||
| Bit | Field | Type | Reset | Description |
|---|---|---|---|---|
| 15-8 | RESERVED | R-0 | 0h | Reserved |
| 7-0 | WDKEY | R/W | 0h | Watchdog Counter Reset Writing 0x55 followed by 0xAA will cause the watchdog counter to reset to zero, preventing an overflow. Writing other values has no effect. Reads of this register return the value of the WDCR register. Reset type: IORSn |
WDCR is shown in Figure 3-50 and described in Table 3-58.
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Watchdog Control Register
| 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 |
| RESERVED | WDPRECLKDIV | ||||||
| R-0-0h | R/W-0h | ||||||
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| RESERVED | WDDIS | WDCHK | WDPS | ||||
| R/W1S-0h | R/W-0h | R-0/W-0h | R/W-0h | ||||
| Bit | Field | Type | Reset | Description |
|---|---|---|---|---|
| 15-12 | RESERVED | R-0 | 0h | Reserved |
| 11-8 | WDPRECLKDIV | R/W | 0h | Watchdog Clock Pre-divider These bits determine the watchdog clock pre-divider, which is the first of the two dividers between SECCLK and the watchdog counter clock (WDCLK). The frequency of WDCLK is given by the formulas: PREDIVCLK = SECCLK / Pre-divider WDCLK = PREDIVCLK / Prescaler The watchdog reset or interrupt pulse is 512 SECCLK cycles long, so the counter period must be longer. To guarantee this, the product of the prescaler and pre-divider must be greater than or equal to four. The default pre-divider value is 512. 0h : PREDIVCLK = SECCLK / 512 1h : PREDIVCLK = SECCLK / 1024 2h : PREDIVCLK = SECCLK / 2048 3h : PREDIVCLK = SECCLK / 4096 4h : Reserved 5h : Reserved 6h : Reserved 7h : Reserved 8h : PREDIVCLK = SECCLK / 2 9h : PREDIVCLK = SECCLK / 4 Ah : PREDIVCLK = SECCLK / 8 Bh : PREDIVCLK = SECCLK / 16 Ch : PREDIVCLK = SECCLK / 32 Dh : PREDIVCLK = SECCLK / 64 Eh : PREDIVCLK = SECCLK / 128 Fh : PREDIVCLK = SECCLK / 256 Reset type: IORSn |
| 7 | RESERVED | R/W1S | 0h | Reserved |
| 6 | WDDIS | R/W | 0h | Watchdog Disable Setting this bit disables the watchdog module. Clearing this bit enables the watchdog module. This bit can be locked by the WDOVERRIDE bit in the SCSR register. The watchdog is enabled on reset. Reset type: IORSn |
| 5-3 | WDCHK | R-0/W | 0h | Watchdog Check Bits During any write to this register, these bits must be written with the value 101 (binary). Writing any other value will immediately trigger the watchdog reset or interrupt. Reset type: IORSn |
| 2-0 | WDPS | R/W | 0h | Watchdog Clock Prescaler These bits determine the watchdog clock prescaler, which is the second of the two dividers between SECCLK and the watchdog counter clock (WDCLK). The frequency of WDCLK is given by the formulas: PREDIVCLK = SECCLK / Pre-divider WDCLK = PREDIVCLK / Prescaler The watchdog reset or interrupt pulse is 512 SECCLK cycles long, so the counter period must be longer. To guarantee this, the product of the prescaler and pre-divider must be greater than or equal to four. The default prescaler value is 1. 0h : WDCLK = PREDIVCLK / 1 1h : WDCLK = PREDIVCLK / 1 2h : WDCLK = PREDIVCLK / 2 3h : WDCLK = PREDIVCLK / 4 4h : WDCLK = PREDIVCLK / 8 5h : WDCLK = PREDIVCLK / 16 6h : WDCLK = PREDIVCLK / 32 7h : WDCLK = PREDIVCLK / 64 Reset type: IORSn |
WDWCR is shown in Figure 3-51 and described in Table 3-59.
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Watchdog Windowed Control Register
| 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 |
| RESERVED | RESERVED | ||||||
| R-0-0h | R-0h | ||||||
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| MIN | |||||||
| R/W-0h | |||||||
| Bit | Field | Type | Reset | Description |
|---|---|---|---|---|
| 15-9 | RESERVED | R-0 | 0h | Reserved |
| 8 | RESERVED | R | 0h | Reserved |
| 7-0 | MIN | R/W | 0h | Watchdog Window Threshold These bits specify the lower limit of the watchdog counter reset window. If the counter is reset via the WDKEY register before the counter value reaches the value in this register, the watchdog immediately triggers a reset or interrupt. Reset type: IORSn |