The MM74C922 and MM74C923 CMOS key encoders provide all the necessary logic to fully encode an array of SPST switches. The keyboard scan can be implemented by either an external clock or external capacitor. These encoders also have on-chip pull-up devices which permit switches with up to 50 kohm on resistance to be used. No diodes in the switch array are needed to eliminate ghost switches. The internal debounce circuit needs only a single external capacitor and can be defeated by omitting the capacitor. A Data Available output goes to a high level when a valid keyboard entry has been made. The Data Available output returns to a low level when the entered key is released, even if another key is depressed. The Data Available will return high to indicate acceptance of the new key after a normal debounce period; this two-key roll-over is provided between any two switches.

An internal register remembers the last key pressed even after the key is released. The 3-STATE outputs provide for easy expansion and bus operation and are LPTTL compatible.

• Fairchild 1,000 piece Budgetary Pricing
• If there is no sample button displayed at the top of the page, please contact one of the Fairchild distributors or your local sales office to obtain samples.
• Top mark packaging information for product MM74C923 is available.

Product	Product status	Eco Status	Pricing*	Package type	Leads	Packing method	Package Drawing	Package Marking Convention**
MM74C923N	Full Production	RoHS Compliant	$8.57	DIP	20	RAIL		Line 1: $Y (Fairchild logo) &Z (Asm. Plant Code) &4 (4-Digit Date Code) &K&P (Marketing Status Code) Line 2: MM74C923N Line 3: INS8246N
MM74C923WM	Full Production	RoHS Compliant	$7.53	SOIC-Wide	20	RAIL		Line 1: $Y (Fairchild logo) &Z (Asm. Plant Code) &2 (2-Digit Date Code) &K Line 2: MM74C923WM
MM74C923WMX	Full Production	RoHS Compliant	$7.53	SOIC-Wide	20	TAPE REEL		Line 1: $Y (Fairchild logo) &Z (Asm. Plant Code) &2 (2-Digit Date Code) &K Line 2: MM74C923WM