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HYB39S64800BT-8 Datasheet(PDF) 11 Page - Infineon Technologies AG |
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HYB39S64800BT-8 Datasheet(HTML) 11 Page - Infineon Technologies AG |
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11 / 53 page  HYB 39S64400/800/160BT(L) 64-MBit Synchronous DRAM Data Book 11 12.99 Power On and Initialization The default power on state of the mode register is supplier specific and may be undefined. The following power on and initialization sequence guarantees the device is preconditioned to each users specific needs. Like a conventional DRAM, the Synchronous DRAM must be powered up and initialized in a predefined manner.During power on, all V DD and VDDQ pins must be built up simultaneously to the specified voltage when the input signals are held in the “NOP” state. The power on voltage must not exceed V DD + 0.3 V on any of the input pins or VDD supplies. The CLK signal must be started at the same time. After power on, an initial pause of 200 µs is required followed by a precharge of both banks using the precharge command. To prevent data contention on the DQ bus during power on, it is required that the DQM and CKE pins be held high during the initial pause period. Once all banks have been precharged, the Mode Register Set Command must be issued to initialize the Mode Register. A minimum of eight Auto Refresh cycles (CBR) are also required.These may be done before or after programming the Mode Register. Failure to follow these steps may lead to unpredictable start-up modes. Programming the Mode Register The Mode register designates the operation mode at the read or write cycle. This register is divided into 4 fields. A Burst Length Field to set the length of the burst, an Addressing Selection bit to program the column access sequence in a burst cycle (interleaved or sequential), a CAS Latency Field to set the access time at clock cycle and a Operation mode field to differentiate between normal operation (Burst read and burst Write) and a special Burst Read and Single Write mode. The mode set operation must be done before any activate command after the initial power up. Any content of the mode register can be altered by re-executing the mode set command. All banks must be in precharged state and CKE must be high at least one clock before the mode set operation. After the mode register is set, a Standby or NOP command is required. Low signals of RAS, CAS, and WE at the positive edge of the clock activate the mode set operation. Address input data at this timing defines parameters to be set as shown in the previous table. Read and Write Operation When RAS is low and both CAS and WE are high at the positive edge of the clock, a RAS cycle starts. According to address data, a word line of the selected bank is activated and all of sense amplifiers associated to the wordline are set. A CAS cycle is triggered by setting RAS high and CAS low at a clock timing after a necessary delay, t RCD, from the RAS timing. WE is used to define either a read (WE = H) or a write (WE = L) at this stage. SDRAM provides a wide variety of fast access modes. In a single CAS cycle, serial data read or write operations are allowed at up to a 133 MHz data rate. The numbers of serial data bits are the burst length programmed at the mode set operation, i.e., one of 1, 2, 4, 8 and full page, where full page is an optional feature in this device. Column addresses are segmented by the burst length and serial data accesses are done within this boundary. The first column address to be accessed is supplied at the CAS timing and the subsequent addresses are generated automatically by the programmed burst length and its sequence. For example, in a burst length of 8 with interleave sequence, if the first address is ‘2’, then the rest of the burst sequence is 3, 0, 1, 6, 7, 4, and 5. Full page burst operation is only possible using the sequential burst type and page length is a function of the I/O organization and column addressing. Full page burst operation do not self |
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