STMicroelectronics PSD834F2-70J

Overview

PSD834F2-70J from STMicroelectronics is a Flash in-system programmable (ISP) peripheral IC for 8-bit microcontrollers, integrating dual-bank Flash (1 Mbit primary + 256 Kbit secondary), 256 Kbit SRAM, 27 reconfigurable I/O ports, and a hybrid PLD (3000-gate CPLD + user-defined DPLD). It supports concurrent read/erase/write operations and is used in legacy industrial control systems requiring field-upgradable firmware and flexible address decoding.

For engineers reviewing the PSD834F2-70J datasheet, PSD834F2-70J pinout, PSD834F2-70J application, or PSD834F2-70J equivalent, key selection criteria include ISP JTAG support, 5 V operation, PLD-based chip select decoding, page register–enabled address expansion, and compatibility with 80C51/68HC11 bus protocols.

Technical Context

The PSD834F2-70J implements a tightly coupled memory-peripheral architecture where the primary Flash (8 × 32K × 8) and secondary Flash (4 × 64K × 8) operate independently under JTAG-controlled ISP. Its PLD subsystem comprises 16 output macrocells (OMCs) and 24 input macrocells (IMCs), enabling custom logic for chip select generation and address latching.

The MCU bus interface supports both multiplexed (e.g., 80C51XA) and non-multiplexed (e.g., 68HC11) 8-bit buses, with dedicated signals for RD/WR, ALE, and CS. The internal page register extends the 8-bit MCU's 64 KB address space by 256× via bank switching, while the Turbo Bit optimizes PLD timing for high-speed decode paths.

Key Specifications

Pinout & Package

PSD834F2-70J is housed in a 52-pin PLCC (Plastic Leaded Chip Carrier) package, ECOPACK®-compliant, with 27 I/O pins distributed across Ports A–D, plus dedicated JTAG (TCK/TMS/TDI/TDO), reset, power, and bus control signals.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Flash-based peripheral expansion applications.

Compared with PSD834F2-70J, PSD833F2-70J reduces Flash capacity and removes concurrent operation-limiting field upgrade flexibility-while PSD854F2-70J retains full functionality but mandates mechanical redesign due to its 64-pin TQFP package and incompatible pin mapping.

Availability

PSD834F2-70J is available at Aetrix Electronics and suitable for industrial PLC I/O modules, legacy automotive ECUs, and medical infusion pump controllers requiring stable component supply and long-term obsolescence management.

Supply support for PSD834F2-70J includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader specializing in microcontrollers, analog ICs, and programmable logic devices for industrial, automotive, and consumer applications.

The PSD8XXFX product line was designed to extend the capabilities of legacy 8-bit MCUs by integrating Flash memory, SRAM, and configurable PLD logic into a single ISP-capable peripheral-targeting cost-sensitive, long-lifecycle embedded systems.

FAQ

What is the maximum operating frequency supported by the PSD834F2-70J?

The PSD834F2-70J is rated for 70 ns access time, corresponding to a maximum bus clock frequency of 14.3 MHz for 80C51-compatible systems and 2 MHz for 68HC11 interfaces. Its internal PLD logic operates synchronously with the MCU bus clock, and timing compliance depends on proper PCB layout and VCC decoupling per STMicroelectronics Application Note AN2292.

Does the PSD834F2-70J support in-system programming without removing it from the target board?

Yes-the device features a fully IEEE 1149.1-compliant JTAG port that enables complete in-system programming of Flash and PLD configuration without physical removal. Programming uses the low-cost FlashLINK cable with standard PC serial or USB-to-serial adapters, and requires no external voltage programming supplies beyond VCC = 5.0 V.

How many sectors can be independently protected in the primary Flash memory?

The primary Flash contains 8 uniform 32K × 8 sectors, each with individual software-controlled protection bits stored in the Flash Protection register (address 0x0000–0x0007). Protection is enforced at power-on and after reset; once locked, a sector cannot be erased or programmed until explicitly unlocked via the JTAG interface using the correct security sequence.

Can the PLD logic be reconfigured independently of Flash programming?

Yes-the CPLD and DPLD logic configurations are stored in separate non-volatile registers and can be updated independently via JTAG without affecting Flash contents. The OMC Mask register (0x0010–0x001F) and PLD configuration bits (0x0020–0x003F) allow runtime redefinition of decode logic, enabling dynamic peripheral remapping during system operation.