1. General description
The 74HC42 is a one of ten BCD to decimal decoder. It accepts four BCD inputs (0A to
3A) and provides ten mutually exclusive outputs (0Y to 9Y). The logic design ensures that
all outputs are HIGH when binary codes greater than nine are applied to the inputs. The
most significant input (3A) produces an useful inhibit function when the device is used as
a 1-of-8 decoder. The 3A input can also be used as the data input in an 8-output
demultiplexer application. Inputs include clamp diodes. This enables the use of current
limiting resistors to interface inputs to voltages in excess of VCC.
2. Features and benefits
 Complies with JEDEC standard no. 7A
 Input levels:
 For 74HC42: CMOS level
 Mutually exclusive outputs
 1-of-8 demultiplexing capability
 Outputs disabled for input codes above nine
 ESD protection:
 HBM JESD22-A114F exceeds 2000 V
 MM JESD22-A115-A exceeds 200 V
 Specified from 40 C to +85 C and 40 C to +125 C