DESCRIPTION AND OPERATIONSLAVE EXPANDER BUSI-E96-301B 2 - 5socket empty or not connecting the MMUs with cables sepa-rates them.Slave Expander Bus InterfaceThe IMASI03 uses a custom gate array for the slave expanderbus interface. An integrated circuit holds all the control logicand communication protocol. This integrated circuit providesthese functions:• Address comparison and detection.• Message decoding and translation.• Data line filtering of bus signals.• On-board bus drivers.• Expander bus watchdog.A dual port RAM (DPRAM) stores data that can be accessed atthe same time by the MFP and the slave's microcontroller.Data ValuesFor all inputs, channel values are adjusted based on the fac-tory calibration and drift correction data. Thermocouple inputsreceive cold junction reference compensation. Nonlinearity andlead wire resistance adjustments are performed when neces-sary. The IMASI03 slave provides drift-corrected values to theMFP master over the slave expander bus. These values are inengineering units.The slave sends a status indication to the MFP master for eachinput channel. This status indicates any hardware errors andchannel configuration errors detected by the slave.Termination UnitsThe IMASI03 uses one NTAI06 termination unit or two NIAI05termination modules to connect to field signals. An NKAS01/11 cable connects the termination unit to the slave through theP3 connector. An NKAS02/12 cable connects the terminationmodule to the slave through the P3 connector. The terminationdevices contain RTDs used for cold junction compensation ofthermocouple inputs. They also contain the circuitry needed toconvert 4-20 mA field signals into the 1-5 V needed to input tothe slave. The system power supply is protected from short cir-cuits by current limiting resistors on the NIAI05 (hardwarerevision A) and by fuses on the NTAI06 and NIAI05 (hardwarerevision B).Function CodesFunction codes 215 and 216 in the master MFP configure theIMASI03 and identify the active analog inputs. One functioncode 215 is required for each IMASI03 slave. One function code216 is required for each input channel used on the slave. Thesefunction codes specify the slave expander bus address of the