20-668-0003 Rabbit Semiconductor, 20-668-0003 Datasheet - Page 222

• Manufacturer Part Number: 20-668-0003
• Description: IC CPU RABBIT2000 30MHZ 100PQFP
• Manufacturer: Rabbit Semiconductor

Specifications of 20-668-0003

• Processor Type: Rabbit 2000 8-Bit
• Speed: 30MHz
• Voltage: 2.7V, 3V, 3.3V, 5V
• Mounting Type: Surface Mount
• Package / Case: 100-MQFP, 100-PQFP
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 30 MHz
• Operating Supply Voltage: 0 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Number Of Programmable I/os: 40
• Number Of Timers: 8 & 10 bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 20-668-0003; 316-1062

When the spectrum spreader is engaged, the frequency is modulated, and individual clock
cycles may be shortened or lengthened by an amount that depends on whether the clock
doubler is engaged and whether the spectrum spreader is set to the normal or strong set-
ting. The frequency modulation amplitude and the change in clock cycle length is greater
at lower voltages or higher temperatures since it is sensitive to process parameters. The
spectrum spreader also introduces a time offset in the system clock edge and an equal off-
set in edges generated relative to the system clock. A feedback system limits the worst-
case time error of any signal edge derived from the system clock to ±35 ns for the normal
setting and ±70 ns for the strong setting at 5.0 V. The maximum time offset is inversely
proportional to operating voltage. This small timing error will not generally affect opera-
tions in the great majority of systems.
If the input oscillator frequency is 4 MHz or less, the spectrum spreader modulation of fre-
quency will enter the audio range of 20 kHz or less, and may generate an audible whistle
in FM stations. For this reason it may be desirable to disable the spreader for low-speed
oscillators (where it is probably unnecessary anyway). However, in practical cases the
whistle may not be audible because of the very low level of the interference from a system
with a low oscillator frequency with the spectrum spreader engaged. Each halving of clock
frequency reduces the amplitude of the harmonics at a given frequency by 6 dB or more.
The effect of pure harmonic noise on an FM station is to either completely block out a sta-
tion near the harmonic frequency or to disturb the reception of that station. If the spectrum
spreader is engaged, the interference will be spread across the band, but will generally be
so low as to be undetectable, except perhaps for extremely weak stations. The effect of a
pure harmonic on TV reception is to create a herringbone pattern created by a harmonic
falling within the station’s band. If the spreader is engaged, the pattern will disappear
216
7
6:0
7
6:0
Bit(s)
Bit(s)
Global Clock Modulator 0 Register
Global Clock Modulator 1 Register
0
1
0
1
Value
Value
Table B-10. Spread Spectrum Enable/Disable Register
Table B-11. Spread Spectrum Mode Select
Enable normal spectrum spreading.
Enable strong spectrum spreading.
These bits are reserved.
Disable the spectrum spreader.
Enable the spectrum spreader.
These bits are reserved.
(GCM0R)
(GCM1R)
Description
Description
Rabbit 2000 Microprocessor User’s Manual
(Address = 0x0A)
(Address = 0x0B)