20-668-0024 Rabbit Semiconductor, 20-668-0024 Datasheet - Page 323

• Manufacturer Part Number: 20-668-0024
• Description: IC CPU RABBIT4000 128-LQFP
• Manufacturer: Rabbit Semiconductor

Specifications of 20-668-0024

• Processor Type: Rabbit 4000 8-bit
• Speed: 60MHz
• Voltage: 2.5V, 2.7V, 3V, 3.3V
• Mounting Type: Surface Mount
• Package / Case: 128-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Other names: 20-668-0022; 316-1078

Similarly, the gross output-enable access time is T + minimum clock low time (it is
assumed that the early output enable option is enabled). This is reduced by the spectrum
spreader loss, the time from clock to output for the output enable signal, the data setup
time, and a correction for the asymmetry of the original oscillator clock.
Example Output-Enable Access Time Calculation
• clock = 29.49 MHz, so T = 34 ns
• operating voltage is 3.3 V
• the clock doubler has a nominal delay of 16 ns (see Table 28-8), resulting in a minimum
• clock to output enable is 5 ns (assuming 20 pF load)
• spectrum spreader is on in 1 ns mode, resulting in a loss of 4.5 ns worst-case (see
• main clock asymmetry is 52% / 48%, resulting in a loss of 4% of the clock period, or
The output enable access time is given by
Chapter 28 Specifications
clock low time of 80% × 16 ns = 12.8 ns
Table 28-9)
1.4 ns
NOTE: There is some process and temperature variation in the clock doubler settings. As
a rule of thumb, a 20% variation should be considered. When the doubler is enabled,
80% of the nominal value should be used for the memory access time calculation.
access time
= T + (min. clock low) - (clock to output enable) -
= 34 ns + 12.8 ns - 5 ns - 4.5 ns - 1.4 ns
= 36 ns
(spreader delay) - (asymmetry delay) - (data setup time)
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