Rabbit 2000, User Manual

Page: 157 / 230

User’s Manual 151
15. AC T
IMING
S
PECIFICATIONS
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
T
adr
output delay with
20 pF address line load
15 ns 11 ns 10 ns 8 ns 7 ns
T
adr
output delay with
70 pF address line load
27 ns 21 ns 19 ns 15 ns 14 ns
T
setup
4 ns 4 ns 3 ns 3 ns 2 ns
T
oe
delay from clock to
output enable (10 pF load)
12 ns 8 ns 8 ns 6 ns 5 ns
2001.01.31