Fluke 123B/S Service Manual - Page 35
Start-up Sequence, Operating Modes, Mask active mode
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3 Circuit Descriptions 3.2 Block Diagram 3.2.5 Start-up Sequence, Operating Modes The test tool sequences through the following steps when power is applied (see also Figure 3-2): 1. The P-ASIC is directly powered by the battery or power adapter voltage VBAT. Initially the Fly Back Converter is off, and the D-ASIC is powered by VBAT via transistor V569 (+3V3GAR). If the voltage +3V3GAR is below 3.05V, the P-ASIC keeps its output signal VGARVAL (supplied to the D-ASIC) low, and the D-ASIC will not start up. The test tool is not working, and is in the Idle mode. 2. If the voltage +3V3GAR is above 3.05V, the P-ASIC makes the line VGARVAL high, and the D-ASIC will start up. The test tool is operative now. If it is powered by batteries only, and not turned on, it is in the Off mode. In this mode the DASIC is active: the real time clock runs, and the ON/OFF key is monitored to see if the test tool will be turned on. 3. If the power adapter is connected (P-ASIC output MAINVAL high), and/or the test tool is turned on, the embedded D-ASIC program, called mask software, starts up. The mask software checks if valid instrument software is present in the Flash ROM's. If not, the test tool does not start up and the mask software continues running until the test tool is turned off, or the power is removed. This is called the Mask active mode. The mask active mode can also be entered by pressing the ^ and > key when turning on the test tool. If valid instrument software is present, one of the following modes will become active: Charge mode The Charge mode is entered when the test tool is powered by the power adapter, and is turned off. The FLY-BACK CONVERTER is off. The CHARGERCONVERTER charges the batteries (if installed). Operational & Charge mode The Operational & Charge mode is entered when the test tool is powered by the power adapter, and is turned on. The FLY-BACK CONVERTER is on, the CHARGER-CONVERTER supplies the primary current. If batteries are installed, they will be charged. In this mode a battery refresh (see below) can be done. Operational mode The Operational mode is entered when the test tool is powered by batteries only, and is turned on. The FLY-BACK CONVERTER is on, the batteries supply the primary current. If the battery voltage (VBAT) drops below 4V when starting up the fly back converter, the Off mode is entered. 3-7