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| 型号： | MC68302FC20CR2 |
| 厂商： | FREESCALE SEMICONDUCTOR INC |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | 4 CHANNEL(S), 10M bps, LOCAL AREA NETWORK CONTROLLER, PQFP132 |
| 封装： | 0.950 X 0.950 INCH, 0.025 INCH PITCH, PLASTIC, QFP-132 |
| 文件页数： | 46/128页 |
| 文件大小： | 641K |
| 代理商： | MC68302FC20CR2 |
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MC68EN302 Module Bus Controller
MOTOROLA
MC68EN302 REFERENCE MANUAL
2-7
2.8 BUS INTERFACE
The MBC is responsible for determining the source of the bus mastership (module bus,
external 68K bus or internal 302 core) and for controlling the direction of the buses. The
layer of buffering between the internal 302 and internal 68000 buses mimics the operation
of the 68302 external bus, giving the module bus the appearance of an external master from
the viewpoint of the internal 302 core. The MBC does not affect the operation of the bus
outside the MC68EN302 unless it arbitrates for that bus and is given bus mastership. The
operation of the MBC as bus master is such that the bus external to the MC68EN302
operates as if an existing 302 peripheral is bus master. This is accomplished by:
Providing I/O control at the pad which overrides the existing 68302 I/O control.
Intercepting the external arbitration signals and merging them with the MBC arbitration.
2.8.1 Bus Arbitration
The MBC provides the circuitry which prioritizes the bus mastership requests in the following
order (highest priority to lowest):
External bus requests
Module bus requests (Ethernet module)
internal 302 core
2.9 DYNAMIC BUS SIZING
The MBC accommodates dynamic bus sizing by providing control to operate on the internal
68000 bus as a 16-bit device while simultaneously providing an 8-bit option externally.
Control is provided via the EN8 bit in the CSER3–CSER0 registers and via the BUSW pin.
The MBC routes data into the proper byte of the word D15–D8, increments the address, and
runs a second bus cycle.
When reading and writing, the MBC will assure proper operation when performing even byte
accesses, even word accesses, and odd byte accesses. Figure 2-4 shows the read cases,
and Figure 2-5 shows the write cases. The even word access is the only case requiring two
bus cycles. When an internal bus cycles is taking place, both AS and the appropriate chip
select will be in operation (except when FAST CYCLES are used). The address is
incremented only in the case of an even address access. Because of this, the address
increment only involves setting A0 to one.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MC68302FC25 | 制造商:MOTOROLA 制造商全称:Motorola, Inc 功能描述:Integrated Multiprotocol Processor User’s Manual |
| MC68302FC25C | 功能描述:IC MPU MULTI-PROTOCOL 132-PQFP RoHS:否 类别:集成电路 (IC) >> 嵌入式 - 微处理器 系列:M683xx 标准包装:2 系列:MPC8xx 处理器类型:32-位 MPC8xx PowerQUICC 特点:- 速度:133MHz 电压:3.3V 安装类型:表面贴装 封装/外壳:357-BBGA 供应商设备封装:357-PBGA（25x25） 包装:托盘 |
| MC68302FE16 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Communications Controller |
| MC68302FE16C | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Communications Controller |
| MC68302FE20 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Communications Controller |
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