DP8421AV-20

Controllers Overview

The DP8421AV-20 is a microCMOS programmable dynamic RAM controller designed for 1 Mbit DRAM arrays. It provides a single-chip interface between DRAM and 8-, 16-, or 32-bit systems, generating all required access control signal timing. The device features an on-chip refresh request clock for automatic array refreshing with internal arbitration against accesses. It includes high capacitance drivers for RAS, CAS, WE, and address lines, along with byte enable signals for writing within word sizes up to 32 bits. The controller supports wait state insertion via WAIT or DTACK outputs and utilizes separate precharge counters for memory interleaving.

Controllers Feature Summary

• On-chip high precision delay line ensures critical DRAM access timing parameters are met.
• Integrated arbitration logic manages refresh cycles and system accesses without external intervention.
• Programmable configuration supports nibble, page, and static column DRAM operations.
• High capacitive drivers eliminate the need for external buffering on control and address lines.

Controllers Applications

• Interface between microprocessors and 1 Mbit dynamic RAM arrays
• Systems requiring automatic DRAM refresh management
• Memory subsystems utilizing byte-write capabilities

Controllers Procurement Notes

Verify component authenticity as this part is obsolete. Confirm package integrity and pin alignment before installation. Review datasheet SNOSBX7A for programming sequences and electrical characteristics. Ensure supply voltage levels match specifications. Check for moisture sensitivity handling requirements during storage and assembly.

Controllers Selection Notes

Select this controller for designs interfacing directly with 1 Mbit DRAMs. It suits applications needing integrated refresh and arbitration. Consider the V68A PLCC package for through-hole mounting. Evaluate system clock frequencies against the 20 MHz specification. Verify compatibility with target microprocessor bus protocols.

Controllers Part Context

This component belongs to the DP8420A/21A/22A family of programmable DRAM controllers. The DP8421A variant specifically targets 1 Mbit memory densities. It shares architectural similarities with the DP8420A (256k) and DP8422A (4M), differing primarily in address line count and supported memory capacity. The AV suffix denotes the 20 MHz speed grade.

Controllers Replacement Considerations

Public confirmed substitute part numbers: None available.