Honeywell 621-1151 Analog Input Board 115V AC 16-pt PLC Module

Honeywell 621-1151 Analog Input Board 115V AC, 16-pt. PLC Module

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When installed in an ungrounded AC control circuit, this module requires a separate connection to L1/+VDC to ensure proper operation. While this connection does not interfere with normal input functionality, it provides critical system balance in applications with ground fault detection. By stabilizing the circuit, it helps prevent false ground fault alarms, ensuring accurate diagnostics.

A battery compartment in the PM contains a size AA lithium dry cell battery which provides backup power to the Memory and Register area. This battery is installed when the PM is shipped. The battery is

front-accessible by removing the BA TIERY coverplate. The output is 3.0 volts and will sustain both the Memory and Register Tables for a minimum of 6 months.

The system's Output Status Data Table contained on the processor printed circuit board accommodates the status of 768 output locations. The output status of real I/0 is contained in locations 0-191 and control relay status in locations 192-767. Timer and counter presets and accumulated values plus other data is contained in the Register Table at addresses 4096-4351 which are 16 bits wide. Figure 3 illustrates the memory distribution. Table 1 describes the system capacities of real I/0, control relay addresses and 16-bit registers.

A separate portion of the data table is reserved for system status information. This information is categorized as system identification, system hardware and system diagnostics. See SYSTEM STATUS TABLE CONTENTS in the APPENDIX. Input status is stored at the individual input modules and is read by the processor during program execution.