From an equivalent Signetics 74180 datasheet:
The ‘180 is a 9-bit parity generator or checker commonly used to detect errors in high speed data transmission or data retrieval systems. Both Even and Odd parity enable inputs and parity outputs are available for generating or checking parity on 8-bits.
True active-HIGH or true active-LOW parity can be generated at both the Even and Odd outputs. True active-HIGH parity is established with Even Parity enable input (PE) set HIGH and the Odd parity enable input (PO) set LOW. True active-LOW parity is established when PE is LOW and PO is HIGH. When both enable inputs are at the same logic level, both outputs will be forced to the opposite logic level.
Parity checking of a 9-bit word (8 bits plus parity) is possible by using the two enable inputs plus an inverter as the ninth data input. To check for true active-HIGH parity, the ninth data input is tied to the PO input and an inverter is connected between the PO and PE inputs. To check for true active-LOW parity, the ninth data input is tied to the PE input and an inverter is connected between the PE and PO inputs.
Expansion to larger word sizes is accomplished by serially cascading the ‘180 in 8-bit increments. The Even and Odd parity outputs of the first stage are connected to the corresponding PE and PO inputs, respectively, of the succeeding stage.
Datasheet (related)
Manufactured: 1976 week 8