8

ICS9147-01

Pins 1 and 2 on the ICS9147-01 serve as dual signal functions

to the device. During initial power-up, they act as input

pins. The logic level (voltage) that is present on these pins at

this time is read and stored into a 4-bit internal data latch. At

the end of Power-On reset, (see AC characteristics for timing

values), the device changes the mode of operations for these

pins to an output function. In this mode the pins produce the

specified buffered clocks to external loads.

To program (load) the internal configuration register for

these pins, a resistor is connected to either the VDD (logic 1)

power supply or the GND (logic 0) voltage potential. A 10

Kilohm(10K) resistor is used to provide both the solid CMOS

programming voltage needed during the power-up

programming period and to provide an insignificant load on

the output clock during the subsequent operating period.

Figs. 1 and 2 show the recommended means of implementing

this function. In Fig. 1 either one of the resistors is loaded

onto the board (selective stuffing) to configure the device’s

internal logic. Figs. 2a and b

provide a single resistor

loading option where either solder spot tabs or a physical

jumper header may be used.

These figures illustrate the optimal PCB physical layout

options. These configuration resistors are of such a large

ohmic value that they do not effect the low impedance clock

signals. The layouts have been optimized to provide as little

impedance transition to the clock signal as possible, as it

passes through the programming resistor pad(s).

Shared Pin Operation -

Input/Output Pins

The ICS9147-01 includes a production test verification

mode of operation. This requires that the FSO and FS1 pins

be programmed to a logic high and the FS2 pin be

programmed to a

logic low(see

Shared Pin Operation

section). In this mode the device will output the following

frequencies.

Note: REF is the frequency of either the crystal connected

between the devices X1and X2 or, in the case of a device

being driven by an external reference clock, the frequency

of the reference (or test) clock on the device’s X1 pin.

Test Mode Operation

Fig. 1

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