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AM53C94 Scheda tecnica(PDF) 1 Page - Advanced Micro Devices |
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AM53C94 Scheda tecnica(HTML) 1 Page - Advanced Micro Devices |
1 / 63 page This document contains information on a product under development at Advanced Micro Devices Inc. The information is intended to help you to evaluate this product. AMD reserves the right to change or discontinue work on this proposed product without notice. Publication# 16506 Rev. C Amendment /0 Issue Date: May 1993 Advanced Micro Devices Am53C94/Am53C96 High Performance SCSI Controller PRELIMINARY DISTINCTIVE CHARACTERISTICS s Pin/function compatible with NCR53C94/53C96 s AMD’s Patented GLITCH EATERTM Circuitry on REQ and ACK inputs s 5 Mbytes per second synchronous SCSI transfer rate s 20 Mbytes per second DMA transfer rate s 16-bit DMA Interface plus 2 bits of parity s Flexible three bus architecture s Single ended SCSI bus supported by Am53C94 s Single ended and differential SCSI bus supported by Am53C96 s Selection of multiplexed or non-multiplexed address and data bus s High current drivers (48 mA) for direct connection to the single ended SCSI bus s Supports Disconnect and Reselect commands s Supports burst mode DMA operation with a threshold of 8 s Supports 3-byte-tagged queuing as per the SCSI-2 specification s Supports group 2 and 5 command recognition as per the SCSI-2 specification s Advanced CMOS process for low power consumption s Am53C94 available in 84-pin PLCC package s Am53C96 available in 100-pin PQFP package GENERAL DESCRIPTION The High Performance SCSI Controller (HPSC) has a flexible three bus architecture. The HPSC has a 16-bit DMA interface, an 8 bit host data interface and an 8-bit SCSI data interface. The HPSC is designed to minimize host intervention by implementing common SCSI se- quences in hardware. An on-chip state machine re- duces protocol overheads by performing the required sequences in response to a single command from the host. Selection, reselection, information transfer and disconnection commands are directly supported. The 16-byte-internal FIFO further assists in minimizing host involvement. The FIFO provides a temporary stor- age for all command, data, status and message bytes as they are transferred between the 16 bit host data bus and the 8 bit SCSI data bus. During DMA operations the FIFO acts as a buffer to allow greater latency in the DMA channel. This permits the DMA channel to be sus- pended for higher priority operations such as DRAM re- fresh or reception of an ISDN packet. Parity on the DMA bus is optional. Parity can either be generated and checked or it can be simply passed through. The patented GLITCH EATER Circuitry in the High Per- formance SCSI Controller detects signal changes that are less than or equal to 15 ns and filters them out. It is designed to dramatically increase system performance and reliability by detecting and filtering glitches that can cause system failure. The GLITCH EATER Circuitry is implemented on the ACK and REQ lines only. These lines often encounter many electrical anomalies which degrade system per- formance and reliability. The two most common are Re- flections and Voltage Spikes. Reflections are a result of high current SCSI signals that are mismatched by stubs, cables and terminators. These reflections vary from ap- plication to application and can trigger false handshake signals on the ACK and REQ lines if the voltage ampli- tude is at the TTL threshold levels. Spikes are generated by high current SCSI signals switching concurrently. On the control signals ( ACK and REQ) they can trigger false data transfers which result in loss of data, addition of random data, double clocking and reduced system reli- ability. AMD’s GLITCH EATER Circuitry helps maintain excellent system performance by treating the glitches. Refer to the diagram on the next page. |
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