SDA9251-2X Datasheet, PDF (4/23 Pages) Siemens Semiconductor Group – 868352-Bit Dynamic Sequential Access Memory for Television Applications (TV-SAM)

SDA 9251-2X
Data Transfer from Latch B to Shift Register B (RB)
The contents of latch B are transferred to shift register B at the falling edge of the read transfer
signal RB. If the timing restrictions between RB and the shift clock SCB are taken into account, a
continuous data flow at output SQB without interrupts is possible. This transfer operation is
independent on all other transfer operations except for a small forbidden time window conditioned
by the memory to latch B transfer.
Data Output A (SQA, SCA, OEA)
Data is shifted out through the serial port A (SQA0 … SQA3) at the rising edge of the shift clock
SCA. After 16 clock cycles new data have to be transferred from latch A to shift register A.
Otherwise data values are cyclically repeated.
Via the output enable OEA the output buffers can be switched into tristate.
The shift clock SCA may be completely independent on the shift clock for port B and C (SCB).
Data Output B (SQB, SCB, OEB)
Data is shifted out through the serial port B (SQB0 … SQB3) at the rising edge of the shift clock
SCB. After 16 clock cycles new data have to be transferred from latch B to shift register B.
Otherwise data values are cyclically repeated. The shift clock SCB is also used for the input port C.
Via the output enable OEB the output buffers can be switched into tristate.
Refresh
Either 256 refresh cycles or read/write cycles on 212 consecutive row addresses have to be
executed within an 8 ms interval to maintain the data in the memory arrays.
A refresh cycle is determined by the mode control bits, see “Addressing and Mode Control”. In the
refresh mode, the row and column addresses are ignored.
It should be noted that the shift registers are also dynamic storage elements and that the data will
be lost unless shifted using clocks SCA, SCB and SCAD within the specified retention time.
Initialization
The device incorporates an on-chip substrate bias generator as well as dynamic circuitry. Therefore
an initial pause of 200 µs is required after power on, followed by eight RE-cycles before proper
device operation is achieved.
Semiconductor Group
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