DS1023

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Applications can read the setting of the DS1023 Delay Line by connecting the serial output pin (Q) to the

serial input (D) through a resistor with a value of 1 to 10 kohms (Figure 2). Since the read process is

destructive, the resistor restores the value read and provides isolation when writing to the device. The

resistor must connect the serial output (Q) of the last device to the serial input (D) of the first device of a

daisy chain (Figure 1). For serial readout with automatic restoration through a resistor, the device used to

write serial data must go to a high impedance state.

To initiate a serial read, latch enable (LE) is taken to a logic 1 while serial clock (CLK) is at a logic 0.

transition of the serial clock (CLK), bit 7 (MSB) is rewritten and bit 6 appears on the output after a time

In the case of a daisy chain, the process must be repeated eight times per package. If the value read is

programmed delay remains unchanged.

Since the DS1023 is a CMOS design, unused input pins (P3 - P7) must be connected to well-defined logic

levels; they must not be allowed to float. Serial output Q/P0 should be allowed to float if unused.

CASCADING MULTIPLE DEVICES (DAISY CHAIN) Figure 1

SERIAL READOUT Figure 2

REFERENCE DELAY

In all delay lines there is an inherent, or “step zero”, delay caused by the propagation delay through the

input and output buffers. In this device the step zero delay can be quite large compared to the delay step

size. To simplify system design a reference delay has been included on chip which may be used to

compensate for the step zero delay. In practice this means that if the device is supplied with a clock, for

example, the minimum programmed output delay is effectively zero with respect to the reference delay.