DS3106LN+【PDF 31/92 页】IC TIMING LINE CARD 64-LQFP

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DS3106

7.10 Reset Logic

The device has three reset controls: the

RST pin, the RST bit in MCR1, and the JTAG reset pin JTRST. The RST

pin asynchronously resets the entire device, except for the JTAG logic. When the

RST pin is low all internal

registers are reset to their default values, including those fields that latch their default values from, or based on, the

states of configuration input pins when the

RST goes high. The RST pin must be asserted once after power-up

while the external oscillator is stabilizing.

The MCR1:RST bit resets the entire device (except for the microprocessor interface, the JTAG logic, and the RST

bit itself), but when RST is active, the register fields with pin-programmed defaults do not latch their values from, or

based on, the corresponding input pins. Instead, these fields are reset to the default values that were latched when

the

RST pin was last active.

Microsemi recommends holding

RST low while the external oscillator starts up and stabilizes. An incorrect reset

condition could result if

RST is released before the oscillator has started up completely.

Important: System software must wait at least 100s after reset (

RST pin or RST bit) is deasserted before

initializing the device as described in Section 7.12.

7.11 Power-Supply Considerations

Due to the DS3106’s dual-power-supply nature, some I/Os have parasitic diodes between a 1.8V supply and a

3.3V supply. When ramping power supplies up or down, care must be taken to avoid forward-biasing these diodes

because it could cause latchup. Two methods are available to prevent this. The first method is to place a Schottky

diode external to the device between the 1.8V supply and the 3.3V supply to force the 3.3V supply to be within one

parasitic diode drop below the 1.8V supply (i.e., VDDIO > VDD - ~0.4V). The second method is to ramp up the 3.3V

supply first and then ramp up the 1.8V supply.

7.12 Initialization

After power-up or reset, a series of writes must be done to the DS3106 to tune it for optimal performance. This

series of writes is called the initialization script. Each DS3106 die revision has a different initialization script. For the

latest initialization scripts contact Microsemi timing products technical support.

Important: System software must wait at least 100s after reset (

RST pin or RST bit) is deasserted before

initializing the device.

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