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15. AC TIMING SPECIFICATIONS
The Rabbit 2000 processor may be operated at voltages between 2.5 V and 5.5 V, and at
temperatures from –40°C to +85°C with use possible use over the range -55°C to +120°C.
Most users will operate the Rabbit at either 5.0 V or 3.3 V. The most computation per watt
is obtained at approximately 3.3 V. The highest practical speed is usually obtained at 5 V.
The Rabbit is available in one version, which has a maximum clock speed of 29.4 MHz over the
industrial temperature range of -40°C to +85°C. The R30 has a maximum clock speed of 18.9
MHz at 3.3 V ±10%. The maximum clock speed is 11.5 MHz at 2.5 V.
If a half-speed crystal is used with the clock doubler to achieve the desired clock speed, the
maximum clock speed must be reduced by 4% to allow for an up to 4% asymmetry (52/48)
in the waveform generated by the oscillator. This is because the clock doubler uses the inter-
mediate edge to generate the double frequency. If the clock doubler is used to double
14.7456 MHz to 29.4912 MHz, the operating temperature should be limited to 70°C.
To optimize power consumption, the usual strategy is to use a supply voltage between 3 V
and 3.5 V, and the clock speed should be adjusted downward as far as feasible. This will
give the maximum computation per watt.
Table 15-1. Rabbit Basic Worst-Case Timings
2.50 V min.
-40°C–
+85°C
3.3 V ±10%
-40°C–
+85°C
3.3V ±5%
-40°C–
+70°C
5.0 V ±10%
-40°C–
+85°C
5.0 V ± 5%
-40°C–
+70°C
Maximum clock speed
11.5 MHz
17.5 MHz
19.25 MHz
29.5 MHz
31.5 MHz
Maximum clock speed
generated using clock
doubler
11.06 MHz
16.75 MHz
18.5 MHz
28.5 MHz
30.0 MHz
Tadr output delay with
20 pF address line load
15 ns
11 ns
10 ns
8 ns
7 ns
Tadr output delay with
70 pF address line load
27 ns
21 ns
19 ns
15 ns
14 ns
Tsetup
4 ns
3 ns
2 ns
Toe delay from clock to
output enable (10 pF load)
12 ns
8 ns
6 ns
5 ns
2001.01.31