Texas Instruments TM248NBK36R-80

Overview

TM248NBK36R-80 from Texas Instruments is a 2,097,152 × 36-bit dynamic RAM module (SIMM) in a 72-pin leadless single in-line package, designed for high-density memory expansion in industrial workstations and embedded computing systems requiring 5-V TTL-compatible DRAM with parity support and enhanced page-mode operation. It integrates sixteen 4-Mbit TMS44400DJ DRAMs and two 4-Mbit TMS44460DJ Quad-CAS DRAMs on a decoupled substrate.

For engineers reviewing the TM248NBK36R-80 datasheet, TM248NBK36R-80 pinout, TM248NBK36R-80 application, or TM248NBK36R-80 equivalent, key selection criteria include RAS access time (80 ns), 16-ms refresh interval, presence detect pins (PD1–PD4), CAS-before-RAS (CBR) refresh capability, and compatibility with 72-pin SIMM sockets supporting 36-bit data width and parity.

Technical Context

The TM248NBK36R-80 implements a double-sided 72-pin SIMM architecture with four independent 2,097,152 × 9-bit memory blocks-each block using nine DRAMs (eight TMS44400DJ + one TMS44460DJ) to deliver 36-bit data plus parity. Row-address strobes RAS2/RAS3 and column-address strobes CAS0–CAS3 are assigned per side to enable interleaved access across both sides.

It supports three timing modes: standard random access (tRAC = 80 ns), page-mode read/write (tPC = 50 ns), and CBR refresh (tREF = 16 ms). All inputs/outputs are fully TTL-compatible, with 3-state outputs controlled by CAS and W signals, and common I/O lines shared across DQ0–DQ35 under early-write-cycle protocol to avoid bus contention.

Key Specifications

Pinout & Package

72-pin leadless single in-line memory module (SIMM), BK-series double-sided construction with tin-lead (solder) contact tabs; substrate includes integrated decoupling capacitors and gold-plated nickel underlayer for reliable socket mating.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar DRAM module applications.

Compared with TM248NBK36B-80, the TM248NBK36R-80 offers identical performance with solder-tab contacts for reflow assembly, while TM124MBK36R-80 provides a pin-compatible but lower-density alternative for capacity-downgraded configurations - all three share the same timing envelope and presence-detect coding scheme.

Availability

TM248NBK36R-80 is available at Aetrix Electronics and suitable for industrial control HMIs, legacy workstation upgrades, and test equipment memory expansion requiring stable component supply, long-lifecycle support, and verified 72-pin SIMM compatibility.

Supply support for TM248NBK36R-80 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

Texas Instruments is a U.S.-based semiconductor manufacturer founded in 1930, specializing in analog, embedded processing, and memory solutions for industrial, communications, and computing markets.

The TM248NBK36R-80 belongs to TI's BK-series SIMM product line, developed in the early 1990s to deliver standardized, socket-compatible DRAM modules for PC/AT-class systems and industrial computers requiring parity-checked, high-density memory with simplified board-level integration.

FAQ

What is the memory capacity and organization of the TM248NBK36R-80?

The TM248NBK36R-80 is organized as 2,097,152 words × 36 bits, delivering 8 MB total capacity. It comprises four independent 2,097,152 × 9-bit blocks - each block using eight 4-Mbit TMS44400DJ DRAMs and one 4-Mbit TMS44460DJ Quad-CAS DRAM - with bit 9 in each 9-bit group allocated for parity. This structure is implemented across a double-sided 72-pin SIMM substrate.

Does the TM248NBK36R-80 support CBR (CAS-before-RAS) refresh?

Yes, the TM248NBK36R-80 fully supports CAS-before-RAS (CBR) refresh mode, as confirmed in its functional description and timing specifications. CBR refresh allows the memory controller to embed refresh cycles within normal read/write operations by asserting CAS before RAS, eliminating the need for dedicated RAS-only refresh cycles and reducing system overhead. The tREF interval remains 16 ms regardless of refresh method.

How does the TM248NBK36R-80 differ from the TM124MBK36R-80?

The TM248NBK36R-80 provides double the memory capacity (8 MB vs. 4 MB) and uses a double-sided PCB layout with sixteen TMS44400DJ and two TMS44460DJ DRAMs, whereas the TM124MBK36R-80 is single-sided with eight TMS44400DJ and one TMS44460DJ. Both share identical 72-pin SIMM packaging, timing (80 ns tRAC), presence detect coding, and electrical interface - but they are not drop-in replacements due to differing RAS/CAS mapping and capacity detection.

What is the purpose of the PD1–PD4 pins on the TM248NBK36R-80?

The PD1–PD4 pins (pins 67–70) on the TM248NBK36R-80 implement presence detect functionality to communicate module identity to the host system. For the -80 speed grade, the datasheet specifies fixed connections: PD1 = VSS, PD2 = VSS, PD3 = NC, PD4 = VSS. This unique voltage pattern allows BIOS or memory controller firmware to automatically detect both the 2M×36 capacity and 80 ns speed rating without manual configuration.

Is the TM248NBK36R-80 compatible with standard 72-pin SIMM sockets?

Yes, the TM248NBK36R-80 is mechanically and electrically compatible with industry-standard 72-pin leadless SIMM sockets designed for 5-V, 36-bit-wide memory modules. Its BK-series double-sided construction, 0.05-inch substrate thickness, nickel/tin-lead contact plating, and pinout conform to JEDEC MO-XX specifications for 72-pin SIMMs. Socket compatibility assumes proper support for presence detect decoding and CBR refresh timing.