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SJ-3544 Datasheet
SJ-3544 Price BUFFER READ: Data can be read from either one of the two buffers, using different opcodes to specify which buffer to read from. An opcode of 54H or D4H is used to read data from buffer l, and an opcode of 56H or D6H is used to read data from buffer 2. To perform a Buffer Read, the eight bits of the opcode must be followed by 15 don't care bits, nine address bits, and eight don't care bits. Since the buffer size is 264 bytes, nine address bits (BFA8 - BFAO) are required to specify the first byte of data to be read from the buffer. The CS pin must remain low during the loading of the opcode, the address bits, the don't care bits, and the reading of data. When the end of a buffer is reached, the device will continue reading back at the beginning of the buffer. A low-to-high transi- tion on the CS pin will terminate the read operation and tri-state the SO pin. SJ-3544 on stock Notes: 1. The internal write time is defined by the overlap of ~E~ LOW, CE2 HIGH and WE LOW. All signals must be in valid states to initiate a Write, but any one can go inactive to terminate the Write. The Data Input Setup and Hold timing are referenced to the rising or falling edge of the signal that terminates the Write. 2. 110 will assume the High-Z state if OE = VIH. Write Buffer Read Merge Monitoring Analysis Conventional write buer architectures do not provide the read merge function, and require the entire buffer to be flushed to SDRAM if a read access occurs to any data that currently exists in the buffer. When this occurs, the read access incurs the overhead associated with the write-back of all buffer contents to SDRAM instead of just the data that is needed to maintain data coherency. However, because the ElanSC520 microcontroller's write buffer provides merging and collapsing, this forced flush on the occurrence of a read access that currently exists in the write buffer is not necessary. The read access continues around the associated write data, and the more current write data is merged in from the write |
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