NXP Semiconductors PCF8584T/2,512

Overview

PCF8584T/2,512 from Philips Semiconductors is a parallel-bus-to-I²C-bus protocol converter IC supporting both master and slave operation, with programmable SCL frequencies up to 90 kHz, −40 to +85 °C operating temperature range, and 4.5–5.5 V supply voltage. It enables 8051-, 68000-, and Z80-based microcontrollers to interface with I²C peripherals in industrial control and embedded instrumentation systems.

For engineers reviewing the PCF8584T/2,512 datasheet, PCF8584T/2,512 pinout, PCF8584T/2,512 application, or PCF8584T/2,512 equivalent, key selection considerations include its dual-mode bus interface detection (80XX/68000), long-distance 4-wire mode support, monitor mode capability, interrupt vector programmability, and register-level control of START/STOP/ACK via S1.

Technical Context

The PCF8584T/2,512 implements full I²C-bus protocol handling-including arbitration, timing, START/STOP generation, and ACK/NACK control-via dedicated internal registers (S0–S3) accessed through an 8-bit parallel port. Its dual-register architecture separates write-only control bits (e.g., STA, STO, ACK) from read-only status flags (e.g., BB, AAS, BER), enabling deterministic polled or interrupt-driven communication.

It supports three specialized operational modes: long-distance (4-wire, requiring external line drivers), monitor (passive bus sniffing with S0' = 0x00), and strobe (monostable pulse on RESET/STROBE pin after address+STOP). Interface mode (80XX vs. 68000) is auto-detected on power-up via WR–CS timing, eliminating manual configuration.

Key Specifications

Pinout & Package

PCF8584T/2,512 is housed in a plastic small outline package (SO20), 20-lead, 7.5 mm body width (SOT163-1), surface-mount compatible with reflow and wave soldering per Philips specification.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I²C-bus controller applications.

Compared with PCA9564 and TCA9564A, the PCF8584T/2,512 offers unique legacy support (80XX/68000 auto-detection), monitor mode, and strobe output - making it irreplaceable in maintenance of aging industrial controllers, whereas the alternatives target modern 400 kHz I²C expansion with better power and ESD performance.

Availability

PCF8584T/2,512 is available at Aetrix Electronics and suitable for industrial sensor hubs, legacy MCU I²C expansion, I²C bus monitoring, and multi-master parallel bus coordination requiring stable component supply and long-term obsolescence management.

Supply support for PCF8584T/2,512 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

Philips Semiconductors (now NXP Semiconductors) is a pioneer in I²C technology, having co-developed the I²C-bus specification and delivered foundational interface ICs for embedded systems.

The PCF8584 product line was designed specifically to bridge legacy parallel-bus microcontrollers to the emerging I²C ecosystem - enabling cost-effective migration without redesigning host firmware or PCB layout.

FAQ

What is the primary function of the PCF8584T/2,512 in a system?

The PCF8584T/2,512 serves as a hardware I²C-bus controller that converts parallel-bus commands from microcontrollers (e.g., 8051, Z80, 68000) into compliant I²C protocol sequences. It handles START/STOP generation, ACK/NACK, arbitration, and timing - offloading these tasks from firmware and ensuring strict adherence to I²C electrical and timing specifications. This makes the PCF8584T/2,512 essential for reliable, deterministic communication with I²C peripherals in resource-constrained or timing-sensitive applications.

Does the PCF8584T/2,512 support both master and slave operation?

Yes, the PCF8584T/2,512 supports full dual-role operation: it can initiate transactions as an I²C master or respond to commands as a slave. As a master, it generates START/STOP conditions and controls clock timing; as a slave, it recognizes its 7-bit address (loaded in S0') and responds with ACK. The Addressed As Slave (AAS) and Bus Busy (BB) status bits in register S1 provide real-time feedback for robust multi-role implementation in the PCF8584T/2,512.

How does the PCF8584T/2,512 handle different microcontroller bus protocols?

The PCF8584T/2,512 automatically detects whether it is interfacing with an 80XX-type (8051/Z80) or 68000-type bus using the WR–CS signal timing sequence at power-up - no configuration register writes are needed. In 80XX mode, RD and WR serve as read/write controls; in 68000 mode, WR becomes R/W and RD becomes open-drain DTACK. This auto-detection is implemented in hardware (IMC logic), ensuring seamless integration across diverse legacy platforms without firmware adaptation for the PCF8584T/2,512.

What are the requirements to enable long-distance mode on the PCF8584T/2,512?

To enable long-distance mode on the PCF8584T/2,512, set ES1 = 1 and ESO = 1 in register S1, and ensure ENI = 0 before entry. This reassigns pins 2–5 to unidirectional signals: SDA OUT, SCL IN, SDA IN, and SCL OUT. External RS422 line drivers/receivers must be used on these lines. The PCF8584T/2,512 must also be isolated from the 4-wire bus during power-up until initialization completes - otherwise, undefined behavior or bus lockup may occur.

Can the PCF8584T/2,512 operate as a passive I²C bus monitor?

Yes, the PCF8584T/2,512 enters monitor mode when the own address register S0' is loaded with 0x00. In this mode, it passively observes all I²C traffic without generating ACK, START, or STOP, and never contends for bus control. Received bytes appear in the read buffer (S0), and the PIN flag toggles per byte to signal arrival - enabling real-time, non-intrusive bus analysis. This capability is intrinsic to the PCF8584T/2,512 and requires no external components.