The Probe Out of Range Shutdown condition can be cleared by pressing <START/STOP> in Local or Program mode, by rotation the mode switch on the front panel to a different position, or by issuing a Device Clear in Remote mode.

3.7 Internal Error Shutdown Conditions

The C4 monitors system health by keeping track of four internal areas; they are:

Processor health

Tracked by watchdog timer

Memory condition

Checked at startup

Setup parameter integrity

Checked continuously

IEEE-488 bus integrity

Checked continuously

The first three items, above, are discussed in sub sections below. The IEEE-488 bus controller is automatically reset if a problem is detected. No message to the user is generated as no data is typically lost in the process.

3.7.1 Watchdog Timer

Should the system become locked due to corruption that causes the processor to continuously malfunction, an independent watchdog timer will cause a full system reset. After a watchdog reset, the display will show

res err

When this occurs, the mode switch must be turned to the OFF position, then back to the desired mode to clear the reset message and continue operation. Internal memory will be the same as it was when the shutdown condition occurred.

3.7.2 Memory signature checking

Each time the C4 is powered up, the system checks a series of memory signature bytes to test the integrity of system memory. If the signature bytes are not correct, the system assumes that memory has been compromised. If this should occur (a normal event any time a memory chip is replaced) all of system memory is reinitialized. All program steps for Program mode are reset to their default values, and all setup parameters are reset to their default values. The display will show

all res

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C4 Manual Rev 7.5.2

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Sigma C4 manual Res err, All res, Internal Error Shutdown Conditions