Programmable DMA Controller The UPD8257 is a Direct Memory Access (DMA) controller manufactured by NEC. Below are the factual specifications, descriptions, and features from Ic-phoenix technical data files:
### **Manufacturer:** NEC (Nippon Electric Company)
### **Specifications:**
- **Type:** DMA (Direct Memory Access) Controller
- **Data Bus Width:** 8-bit
- **Address Bus Width:** 16-bit
- **Number of DMA Channels:** 4
- **Operating Voltage:** Typically +5V
- **Clock Frequency:** Compatible with standard microprocessor clock speeds (exact frequency depends on the version)
- **Package Type:** Likely DIP (Dual In-line Package) or similar, depending on variant
### **Descriptions:**
- The UPD8257 is designed to facilitate high-speed data transfers between memory and I/O devices without CPU intervention.
- It is commonly used in microprocessor-based systems to improve data transfer efficiency.
- The chip supports four independent DMA channels, allowing multiple peripherals to transfer data simultaneously.
### **Features:**
- **Four Independent DMA Channels:** Enables concurrent data transfers for multiple devices.
- **Cascadable Design:** Can be used in systems requiring more than four DMA channels by cascading multiple controllers.
- **Programmable Priority Modes:** Supports fixed or rotating priority schemes for DMA requests.
- **Auto-Initialization:** Allows DMA channels to reload initial parameters automatically after a transfer completes.
- **Memory-to-Memory Transfer Support:** Some variants may support memory-to-memory DMA operations.
- **Compatibility:** Works with popular microprocessors of its era, such as the Intel 8080/8085 and similar 8-bit CPUs.
This information is based on the available technical documentation for the UPD8257. For exact details, refer to the official NEC datasheet.
