20-668-0024 Rabbit Semiconductor, 20-668-0024 Datasheet - Page 26

• 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

When the clock doubler is used and there is no subsequent division of the clock, the output
clock will be asymmetric, as shown in Figure 2-3.
The doubled-clock low time is subject to wide (50%) variation since it depends on process
parameters, temperature, and voltage. The times given above are for a core supply voltage
of 1.8 V and a temperature of 25°C. The values increase or decrease by 1% for each 5°C
increase or decrease in temperature. The doubled clock is created by xor’ing the delayed
and inverted clock with itself. If the original clock does not have a 50-50 duty cycle, then
alternate clocks will have a slightly different length. Since the duty cycle of the built-in
oscillator can be as asymmetric as 52% / 48%, the clock generated by the clock doubler
will exhibit up to a 4% variation in period on alternate clocks. Memory access time is not
affected because memory bus cycle is 2 clocks long and includes both a long and a short
16
Oscillator delayed
Example
Write
Cycle
Example
Read
Cycle
Doubled clock
and inverted
Delay
time
Oscillator
Address / CS
Address / CS
Early output enb
option
Early write pulse
option
Write pulse
Output enb
Figure 2-3. Effect of Clock Doubler
Data out
0.48P
48%
P
52%
0.52P
0.48P
Rabbit 4000 Microprocessor User’s Manual
0.52P
Data out from mem