Signetics SCN2653 (SCN2653AC4N16C) Polynomial Generator Checker (PGC)
Comparator circuit that complements a receiver/transmitter (R/T or USART/USRT/UART) in the support of character oriented data link controls. Parallel data characters transferred between the CPU and R/T are monitored by the PGC which performs block check character (BCG) and parity (VRG) generation/checking, single character detection, and two character sequence detection.
Datasheet: bitsavers.org/components/signetics/_dataBooks/1986_Signetics_Microprocessor.pdf
