20-668-0011 Rabbit Semiconductor, 20-668-0011 Datasheet - Page 158

• Manufacturer Part Number: 20-668-0011
• Description: IC MPU RABIT3000A 55.5MHZ128LQFP
• Manufacturer: Rabbit Semiconductor

Specifications of 20-668-0011

• Processor Type: Rabbit 3000 8-Bit
• Speed: 55.5MHz
• Voltage: 2.5V, 2.7V, 3V, 3.3V
• Mounting Type: Surface Mount
• Package / Case: 128-LQFP
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 55.5 MHz
• Operating Supply Voltage: 1.8 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 55 C
• Number Of Programmable I/os: 56
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 316-1061

Figure 18-2 shows the adjustment ranges and output clock for the different modes of
operation of the DPLL. Each mode of operation will be described in turn.
Figure 18-2. Adjustment Ranges and Output Clock for Different DPLL Modes
With NRZ and NRZI encoding, all transitions occur on bit-cell boundaries and the data
should be sampled in the middle of the bit cell. If a transition occurs after the expected bit-
cell boundary (but before the midpoint), the DPLL needs to lengthen the count to line up
the bit-cell boundaries. This corresponds to the “add one” and “add two” regions shown. If
a transition occurs before the bit-cell boundary (but after the midpoint), the DPLL needs to
shorten the count to line up the bit-cell boundaries. This corresponds to the “subtract one”
and “subtract two” regions shown. The DPLL makes no adjustment if the bit-cell boundaries
are lined up within one count of the divide-by-16 counter. The regions that adjust the
count by two allow the DPLL to synchronize faster to the data stream when starting up.
With biphase-level encoding, there is a guaranteed “clock” transition at the center of every
bit cell and optional “data” transitions occur at the bit cell boundaries. The DPLL only
uses the clock transitions to track the bit-cell boundaries by ignoring all transitions occur-
ring outside a window around the center of the bit cell. This window is half a bit cell wide.
Additionally, because the clock transitions are guaranteed, the DPLL requires that they
always be present. If no transition is found in the window around the center of the bit cell
for two successive bit cells, the DPLL is not in lock and immediately enters the search
mode. The search mode assumes that the next transition seen is a clock transition and
immediately synchronizes to this transition. No clock output is provided to the receiver
during the search operation. Decoding biphase-level data requires that the data be sampled
at either the quarter or three-quarter point in the bit cell. The DPLL here uses the quarter
point to sample the data.
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Rabbit 3000 Microprocessor User’s Manual