Renesas 72V8981JG

Overview

IDT72V8981JG from Integrated Device Technology (now Renesas) is a 3.3 V ST-BUS®-compatible digital time slot interchange (TSI) switch implementing a non-blocking 128 × 128 channel matrix for telecom voice/data multiplexing. It supports four 2.048 Mb/s serial input (RX0–RX3) and four 2.048 Mb/s serial output (TX0–TX3) streams, each carrying 32 × 64 Kbit/s channels, with microprocessor-controlled routing via 8-bit parallel bus (D0–D7), address lines A0–A5, and control signals CS/DS/R/W. Used in PCM-based digital switching systems including PBX, access concentrators, and TDM cross-connects.

For engineers reviewing the IDT72V8981JG datasheet, IDT72V8981JG pinout, IDT72V8981JG application, or IDT72V8981JG equivalent, key selection criteria include ST-BUS® frame alignment (F0i, C4i = 4.096 MHz), per-channel connection memory control (CMH/CML), ODE-driven three-state TX outputs, 3.3 V I/O with 5 V tolerant inputs, and PLCC-44 packaging with documented pin mapping and timing constraints for processor bus and serial stream interfaces.

Technical Context

The IDT72V8981JG implements dual-mode switching: Connection Mode routes data from Data Memory using addresses stored in Connection Memory Low (CML), enabling broadcast and flexible time-slot mapping; Processor Mode outputs CML contents directly to TX streams under CPU control. Internal serial-to-parallel and parallel-to-serial conversion operates on 125 µs ST-BUS® frames containing 32 × 8-bit slots, with fixed 2.048 Mb/s data rate per RX/TX stream.

Routing is managed via 16-bit Connection Memory split into high/low bytes-CMH controls per-channel mode (Processor/Connection), output enable, and source stream/channel addressing; CML holds either data (Processor Mode) or source address (Connection Mode). Delay through the device ranges from two to multiple channel slots depending on RX/TX stream pairing, with minimum delay achievable only for specific input-output combinations per Table 1.

Key Specifications

Pinout & Package

Package: 44-pin Plastic Leaded Chip Carrier (PLCC), J44-1 footprint, 0.05 inch pitch, 0.65 inch × 0.65 inch body size. Pin 1 index corner marked. DNC (Do Not Connect) pins are unused and must remain unconnected.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar time slot interchange applications.

Compared with IDT72V8981JG, IDT72V8982JG offers identical functionality with extended temperature rating-ideal for harsh environments-while MC145506P provides a lower-density, 5 V alternative lacking ST-BUS® support and requiring redesign of control firmware and clocking infrastructure.

Availability

IDT72V8981JG is available at Aetrix Electronics and suitable for PCM switching, digital loop carrier nodes, ISDN PRI gateways, and TDM-over-IP edge converters requiring stable component supply and long-lifecycle support.

Supply support for IDT72V8981JG 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

Integrated Device Technology, Inc. (IDT), now part of Renesas Electronics Corporation, designed high-performance timing, memory, and interconnect solutions for communications infrastructure.

IDT72V8981JG belongs to IDT's Telecom TSI Switch family, engineered specifically for ST-BUS®-based PCM digital switching in carrier-class access and enterprise telephony systems.

FAQ

What is the primary function of the IDT72V8981JG in a telecom system?

The IDT72V8981JG serves as a 128 × 128 time slot interchange switch that routes individual 64 Kbit/s PCM channels between eight ST-BUS® serial streams (four RX, four TX). It enables non-blocking, software-configurable time-slot mapping for applications like PBX switching, digital loop carriers, and ISDN gateways-operating at 2.048 Mb/s with precise 125 µs frame alignment synchronized to F0i and C4i inputs. Its role is to replace discrete crosspoint switches and FIFOs in TDM fabric designs.

Does the IDT72V8981JG support both Connection Mode and Processor Mode simultaneously?

No-the IDT72V8981JG operates in either Connection Mode or Processor Mode globally, controlled by bit 6 (PE) of the Control Register. When PE = 1, all TX channels output Connection Memory LOW (CML) contents directly; when PE = 0, each channel's behavior is determined individually by bit 2 (CS) of its corresponding Connection Memory HIGH (CMH) location. The IDT72V8981JG does not allow mixed-mode operation per channel without firmware-level toggling of PE or CMH bits.

How does the ODE pin interact with per-channel output enable settings in the IDT72V8981JG?

The ODE pin acts as a global override: when ODE = LOW, all TX0–TX3 outputs enter high-impedance state regardless of CMH bit 0 values. When ODE = HIGH, CMH bit 0 determines per-channel output enable-HIGH enables the driver, LOW places that specific channel in high-Z. This two-level control allows safe power-up initialization (ODE held LOW) followed by granular channel activation in the IDT72V8981JG, preventing bus contention in matrix configurations.

What is the minimum achievable delay between an input and output channel in the IDT72V8981JG?

The minimum delay through the IDT72V8981JG is two channel slots, achievable only for specific RX-to-TX stream pairings listed in Table 1 of the datasheet (e.g., RX0 → TX1, RX1 → TX3). This delay arises from internal serial-to-parallel conversion, memory storage, and parallel-to-serial reconstruction. Delay increases for other combinations due to memory addressing order and stream queuing-designers must consult Table 1 and verify timing in their specific RX/TX mapping to meet real-time constraints in echo cancellation or tandem-free operation.

Can the IDT72V8981JG interface directly with a 5 V microcontroller without level shifting?

Yes-the IDT72V8981JG features 5 V tolerant digital inputs (A0–A5, CS, DS, R/W, F0i, C4i, RX0–RX3), allowing direct connection to 5 V microcontrollers or FPGAs. However, outputs (D0–D7, TX0–TX3, DTA) are 3.3 V LVTTL and must not drive 5 V loads without translation. For bidirectional processor bus operation, external level-shifting is required on D0–D7 if the microcontroller lacks 3.3 V-tolerant I/O; RX/TX streams may require AC coupling or line drivers depending on downstream receiver thresholds.