 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
COP888CF Datasheet(PDF) 31 Page - National Semiconductor (TI) |
|
|
||||||||||||||||||||||||||||||
COP888CF Datasheet(HTML) 31 Page - National Semiconductor (TI) |
|
|
31 / 44 page  WATCHDOG Operation (Continued) TABLE 6. WATCHDOG Service Actions Key Window Clock Action Data Data Monitor Match Match Match Valid Service: Restart Service Window Don’t Care Mismatch Don’t Care Error: Generate WATCHDOG Output Mismatch Don’t Care Don’t Care Error: Generate WATCHDOG Output Don’t Care Don’t Care Mismatch Error: Generate WATCHDOG Output WATCHDOG AND CLOCK MONITOR SUMMARY The following salient points regarding the WATCHDOG and CLOCK MONITOR should be noted: • Both the WATCHDOG and Clock Monitor detector circuits are inhibited during RESET. • Following RESET, the WATCHDOG and CLOCK MONI- TOR are both enabled, with the WATCHDOG having the maximum service window selected. • The WATCHDOG service window and Clock Monitor enable/disable option can only be changed once, during the initial WATCHDOG service following RESET. • The initial WATCHDOG service must match the key data value in the WATCHDOG Service register WDSVR in or- der to avoid a WATCHDOG error. • Subsequent WATCHDOG services must match all three data fields in WDSVR in order to avoid WATCHDOG er- rors. • The correct key data value cannot be read from the WATCHDOG Service register WDSVR. Any attempt to read this key data value of 01100 from WDSVR will read as key data value of all 0’s. • The WATCHDOG detector circuit is inhibited during both the HALT and IDLE modes. • The Clock Monitor detector circuit is active during both the HALT and IDLE modes. Consequently, the device in- advertently entering the HALT mode will be detected as a Clock Monitor error (provided that the Clock Monitor en- able option has been selected by the program). • With the single-pin R/C oscillator mask option selected and the CLKDLY bit reset, the WATCHDOG service win- dow will resume following HALT mode from where it left off before entering the HALT mode. • With the crystal oscillator mask option selected, or with the single-pin R/C oscillator mask option selected and the CLKDLY bit set, the WATCHDOG service window will be set to its selected value from WDSVR following HALT. Consequently, the WATCHDOG should not be serviced for at least 2048 instruction cycles following HALT, but must be serviced within the selected window to avoid a WATCHDOG error. • The IDLE timer T0 is not initialized with RESET. • The user can sync in to the IDLE counter cycle with an IDLE counter (T0) interrupt or by monitoring the T0PND flag. The T0PND flag is set whenever the thirteenth bit of the IDLE counter toggles (every 4096 instruction cycles). The user is responsible for resetting the T0PND flag. • A hardware WATCHDOG service occurs just as the de- vice exits the IDLE mode. Consequently, the WATCH- DOG should not be serviced for at least 2048 instruction cycles following IDLE, but must be serviced within the se- lected window to avoid a WATCHDOG error. • Following RESET, the initial WATCHDOG service (where the service window and the CLOCK MONITOR enable/ disable must be selected) may be programmed anywhere within the maximum service window (65,536 instruction cycles) initialized by RESET. Note that this initial WATCH- DOG service may be programmed within the initial 2048 instruction cycles without causing a WATCHDOG error. Detection of Illegal Conditions The device can detect various illegal conditions resulting from coding errors, transient noise, power supply voltage drops, runaway programs, etc. Reading of undefined ROM gets zeros. The opcode for soft- ware interrupt is zero. If the program fetches instructions from undefined ROM, this will force a software interrupt, thus signaling that an illegal condition has occurred. The subroutine stack grows down for each call (jump to sub- routine), interrupt, or PUSH, and grows up for each return or POP. The stack pointer is initialized to RAM location 06F Hex during reset. Consequently, if there are more returns than calls, the stack pointer will point to addresses 070 and 071 Hex (which are undefined RAM). Undefined RAM from ad- dresses 070 to 07F Hex is read as all 1’s, which in turn will cause the program to return to address 7FFF Hex. This is an undefined ROM location and the instruction fetched (all 0’s) from this location will generate a software interrupt signaling an illegal condition. Thus, the chip can detect the following illegal conditions: 1. Executing from undefined ROM 2. Over “POP”ing the stack by having more returns than calls. When the software interrupt occurs, the user can re-initialize the stack pointer and do a recovery procedure before restart- ing (this recovery program is probably similar to that follow- ing reset, but might not contain the same program initializa- tion procedures). www.national.com 31 |
Similar Part No. - COP888CF |
|
Similar Description - COP888CF |
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
