CDP1871A

• Directly Interfaces with CDP1800-Series Microprocessor
• Low Power Dissipation
• Three-State Outputs
• Scans and Generates Code for 53 Key ASCII Keyboard Plus 32 HEX Keys (SPST Mechanical Contact Switches)
• Shift, Control, and Alpha Lock Input
• RC-Controlled Debounce Circuitry
• Single Supply 4V to 10.5V . . . . . . . . . . . . . (CDP1871A)
                        4V to 6.5V . . . . . . . . . . . . . (CDP1871AC)
• N-Key Lockout

The CDP1871A is a keyboard encoder designed to directly interface between a CDP1800-series microprocessor and a mechanical keyboard array, providing up to 53 ASCII coded keys and 32 HEX coded keys, as shown in the system diagram (Figure 1).

CDP1871A keyboard may consist of simple single-pole single-throw (SPST) mechanical switches. Inputs are provided for alpha-lock, control, and shift functions, allowing 160 unique codes. An external R-C input is available for user-selectable debounce times. The Nkey lock-out feature prevents unwanted key codes if two or more keys are pressed simultaneously.

The CDP1871A and CDP1871AC are functionally identical. They differ in that the CDP1871A has a recommended operating voltage range of 4V to 10.5V, and the CDP1871AC has a recommended operating voltage range 4V to 6.5V. These types are supplied in 40 lead dual-in-line ceramic packages (D suffix), and 40 lead dual-in-line plastic packages (E suffix), and 44 lead plastic chip-carrier packages (Q suffix).