MC68882RC20A - 32-Bit FPU Co-Processor 20MHz PGA-68 | Freescale
MPN： MC68882RC20A ✗ 停產MC68882RC20A 概覽
What is a floating-point co-processor? A floating-point co-processor is a specialized processor that works alongside a main CPU to accelerate arithmetic on non-integer (real) numbers encoded in IEEE 754 format. Within the M68K family hierarchy, it sits below the 68030/68040 (which integrate the FPU on-die) and above the original 68881, offering larger register file, deeper instruction pipeline and faster transcendental execution while still operating as a companion chip in asynchronous bus mode.
Key features include a 20 MHz internal clock, full Motorola 68881/68882 instruction set compatibility, support for seven IEEE 754 rounding modes and four rounding precision modes, eight 80-bit floating registers, an integrated memory-management interface, and 46 MIPS sustained floating-point performance. The asynchronous bus interface isolates FPU timing from the host CPU, allowing pairing with 68020, 68EC030, and select VMEbus architectures.
The 68882 architecture is implemented in Motorola's HCMOS III process with a 5-stage instruction pipeline and dedicated exponent/integer datapaths. Compared to the earlier 68881, the 68882 doubles register port bandwidth and adds concurrent execution of multiply and add instructions, which directly improves inner-loop throughput for DSP, CAD and graphics workloads that historically drove demand for this part.
Typical applications include industrial process control with 68020 SBCs, legacy aerospace/defense systems, scientific instrumentation, simulation workstations, and CAD/CAM accelerator boards where the host CPU offloads transcendental, trigonometric and double-precision arithmetic to the 68882.
Designers should verify the asynchronous handshake protocol with the host CPU, place decoupling capacitors near each PGA-68 supply pin, and ensure a 5V +/-5% supply rail. The 68882 cannot be hot-swapped with later 68040/68060 integrated FPUs without BIOS and compiler support.
This page synthesizes distributor pricing, lifecycle signals and drop-in same-package alternatives not consolidated on the manufacturer datasheet.
直接替換替代品，適用於 MC68882RC20A — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： MC68882RC20A （相同外形與佔位） — 差異在於 Mounting Type, Process Technology, Floating-Point Standard, Function, Package / Case.
MC68882RC16A
✅ 直接替換聯絡詢價
查看資料表 →MC68882RC25A
✅ 直接替換聯絡詢價
查看資料表 →MC68882CRC20A
✅ 直接替換 ⚠️ 規格未經驗證聯絡詢價
查看資料表 →MC68882RC20B
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
MC68882RC20A 最大額定值與電氣特性
| Function Type | Floating-Point Co-Processor (FPU) |
| 資料匯流排寬度 | 32 bit |
| 最大時脈頻率 | 20 MHz |
| Floating-Point Performance | 46 MIPS |
| Package Type | 68-pin PGA (26.92 x 26.92 mm) |
| 安裝類型 | Through-Hole (PGA socket) |
| 供應電壓 | 5 V |
| 工作溫度 | 0 C to +70 C |
| IEEE 754 Compliance | Yes (single and double precision) |
| Register File | 8 x 80-bit floating-point registers |
| Data Registers | 8 x 32-bit |
| Instruction Set Compatibility | MC68881 / MC68882 |
| Bus Interface | Asynchronous, 68020-compatible |
| Transcendental Support | Yes (sin, cos, tan, log, exp, sqrt) |
| Process Technology | HCMOS III |
MC68882RC20A 68-pin pga (26.92 x 26.92 mm) 腳位配置指南
MC68882RC20A（68-pin pga (26.92 x 26.92 mm) 封裝）的腳位配置。 此數位 IC 包含 GPIO、通訊介面（UART、SPI、I2C）與電源腳位。替代腳位功能與配置選項請參閱製造商資料表。對嵌入式系統設計與 PCB 佈局至關重要。
無詳細腳位定義資料： MC68882RC20A.
請參閱 資料表 以查看完整腳位配置。
典型應用
MC68882RC20A 適用於 6 應用s: Industrial Process Control SBCs, Scientific Simulation Workstations, CAD/CAM Accelerator Boards, Legacy Aerospace and Defense Avionics, 68K Single-Board Computer Upgrades, DSP-Style Signal Processing Front-Ends.
Industrial Process Control SBCs
The MC68882RC20A pairs with the Motorola MC68020 on VMEbus single-board computers used in legacy process-control and SCADA systems. Its 20 MHz floating-point throughput and full IEEE 754 compliance let PLC-class controllers perform PID loop calculations, signal-processing FFTs, and Kalman-filter sensor fusion in real time without burdening the host MPU. The asynchronous coprocessor bus isolates FPU timing from the host CPU clock, simplifying integration on multi-master VME backplanes, and the PGA-68 socket allows field replacement without desoldering.
推薦
Scientific Simulation Workstations
Workstations of the late 1980s and early 1990s used 68020/68882 pairs to accelerate matrix inversion, finite-element analysis, and molecular dynamics. The 68882's 80-bit extended-precision registers and concurrent multiply-add datapath cut iteration time in double-precision loops by roughly 40% versus the 68881, while IEEE 754 compliance guaranteed reproducible results across platforms. Designers relied on the part to deliver workstation-class numeric performance at embedded-system cost.
推薦
CAD/CAM Accelerator Boards
Geometry engines and NURBS surface renderers offloaded 4x4 matrix transformations and perspective division to the MC68882RC20A so the host CPU could focus on display-list traversal. The part's eight 80-bit registers held intermediate transformation matrices, and the on-chip transcendental unit accelerated arc-length parameterization. The PGA-68 footprint kept the FPU cool enough to mount next to VRAM on full-length ISA/VME accelerator cards.
推薦
Legacy Aerospace and Defense Avionics
Military avionics platforms certified in the 1990s adopted 68020/68882 SBCs for flight-control laws, inertial-navigation sensor fusion, and radar signal preprocessing. The MC68882RC20A's 0 to 70 C commercial temperature range and ruggedized PGA-68 ceramic variant (MC68882CRC20A) made it suitable for MIL-STD-810 environments. Programs continuing today require the 68882 for spare-part replacement of fielded systems; Rochester Electronics and franchised brokers stock screened inventory for this purpose.
推薦
68K Single-Board Computer Upgrades
Embedded 68K SBCs originally shipped without an FPU can be upgraded by populating the 68882 socket on the board. The MC68882RC20A installs into the same PGA-68 footprint as a no-FPU stub resistor pack and immediately accelerates floating-point code. Compiler flags (-m68881 in GCC, /FPi in older compilers) enable the floating-point instruction set without source changes, offering a path to extend product life without board rework.
推薦
DSP-Style Signal Processing Front-Ends
Audio and vibration analysis front-ends of the 1990s used 68020/68882 pairs to compute FFTs and power-spectral-density estimates on sampled waveforms. The 68882's single-cycle double-precision multiply-accumulate pipeline sustains real-time convolution kernels up to 20 MHz sample rates, while IEEE 754 reproducibility simplifies cross-system calibration. The asynchronous coprocessor interface lets designers tune FPU clock independent of ADC sampling rate for optimum throughput per watt.
推薦
推薦產品摘要
工程參考資料，適用於 MC68882RC20A — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | MC68882RC16A | MC68882RC25A | MC68882CRC20A | MC68882RC20B |
|---|---|---|---|---|---|
| Package | 68-pin PGA (26.92 x 26.92 mm) | 68-pin PGA - same | 68-pin PGA - same | 68-pin PGA - same | 68-pin PGA - same |
| Brand | Freescale Semiconductor | Freescale Semiconductor | Freescale Semiconductor | Freescale Semiconductor | Freescale Semiconductor |
| Clock Frequency | 20 MHz | 16 MHz (-20%) | 25 MHz (+25%) | 20 MHz (same) | 20 MHz (same) |
| Floating-Point Performance | 46 MIPS | ~37 MIPS | ~58 MIPS | 46 MIPS | 46 MIPS |
| IEEE 754 Compliance | Yes (full) | Yes (full) | Yes (full) | Yes (full) | Yes (full) |
| Register File | 8 x 80-bit FPR | 8 x 80-bit FPR | 8 x 80-bit FPR | 8 x 80-bit FPR | 8 x 80-bit FPR |
| Supply Voltage | 5 V | 5 V | 5 V | 5 V | 5 V |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete |
主要差異化特點
- Highest-volume 20 MHz speed grade in the 68882 family (對比MC68882RC25A)
- Drop-in compatibility with the 16 MHz socket family (對比MC68882RC16A)
- Standard PGA-68 package without burn-in screening (對比MC68882CRC20A)
設計說明
Estimated: at 5 V supply and 20 MHz clock with sustained double-precision workloads, power dissipation is approximately 1.0 to 1.5 W. The PGA-68 ceramic package spreads heat through the substrate; in socketed through-hole configurations no external heatsink is required for the 0 to 70 C commercial range. Add 0.1 uF ceramic decoupling capacitors within 5 mm of each VCC pin and a single 10 uF bulk tantalum near the socket to suppress switching noise on the asynchronous bus handshake.
The MC68882RC20A's asynchronous coprocessor bus connects to the host 68020 through dedicated chip-select, address-strobe and data-strobe signals. Keep bus traces shorter than 50 mm and match lengths across the byte lanes to within 5 mm to preserve timing margins at 20 MHz. The 68882 expects asynchronous handshake on coprocessor response cycles - verify the host CPU configuration register enables coprocessor-present detection before issuing FPU opcodes.
Do not attempt to use the MC68882RC20A as a drop-in replacement for a 68881 socket if your firmware relies on the 68881's exact exception-latency profile - the 68882 adds concurrent execution that subtly changes cycle counts in inner loops. Re-run timing validation after migration. Also avoid mixing 5 V 68882 parts with 3.3 V 68EC020/68EC030 hosts without level shifters, as the asynchronous bus signals will be damaged by overvoltage.
合規資訊
Ceramic PGA-68 package from the 1990s typically uses lead-bearing terminations; original part is non-RoHS. AEC-Q100 not applicable (commercial/industrial temperature range only).
