SDA9251-2X Datasheet, PDF (3/23 Pages) Siemens Semiconductor Group – 868352-Bit Dynamic Sequential Access Memory for Television Applications (TV-SAM)

SDA 9251-2X
Data Input (SDC, SCB)
Data are shifted in through the serial port C (SDC0, …, SDC3) at the rising edge of the shift clock
SCB. After16 clock pulses the data have to be transferred from shift register C to latch C. If more
than 16 clock pulses occur before latching the data, only the last sixteen 4-bit data values are
accepted.
Data Transfer from Shift Register C to Latch C (WT)
The contents of the shift register C are transferred to latch C at the falling edge of the write transfer
signal WT. If the timing restrictions between WT and the clock SCB are respected, a continuous
data flow at input SDC is possible without loosing data. This transfer operation may be
asynchronous to all other transfer operations except for a small forbidden window conditioned by
the latch C to memory transfer, see diagram 4.
Write Transfer from Latch C to Memory (RE)
The data of latch C are transferred to the preaddressed location of the memory array at the rising
edge of RE, if the mode bits were set to H (M1) and L (M0), see “Addressing and Mode Control.”
Addressing and Mode Control (SAR, SAC, SCAD, RE)
The serial 8-bit row address SAR and the 8-bit column address/mode code SAC are serially shifted
into the TV-SAM (LSB first) at rising edge of the address clock SCAD. After 8 SCAD cycles, the
falling edge of RE internally latches SAR and SAC. The column address itself needs only 6 bits. The
last 2 bits of SAC are defined as mode bits and determine the read/write and refresh operation of
the memory arrays to be triggered by the RE signal.
Mode Bit M1
L
L
H
H
Mode Bit M0
L
H
L
H
Operation
Read transfer from memory to latch A
Read transfer from memory to latch B
Write transfer from latch C to memory
Refresh with internal row address
Read Transfer from Memory to Latch A or B (RE)
Memory data from a preaddressed location are transferred to latch A or B at the falling edge of RE,
depending on the mode control bits, see “Addressing and Mode Control”.
Data Transfer from Latch A to Shift Register A (RA)
The contents of latch A are transferred to shift register A at the falling edge of the read transfer
signal RA. If the timing restrictions between RA and the shift clock SCA are taken into account, a
continuous data flow at output SQA 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 A transfer.
Semiconductor Group
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