20-668-0024 Rabbit Semiconductor, 20-668-0024 Datasheet - Page 22

• 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

2.3 Operation
2.3.1 Main Clock
The main clock is input on the CLKI pin, and is optionally sent through the spectrum
spreader and then the clock doubler. Both of these are described in greater detail below.
Different main clock modes may be selected via the GCSR, as shown in Table 2-1. Note
that one GCSR setting slows the processor clock while the peripheral clock operates at full
speed; this allows some power reduction while keeping settings like serial baud rates and
the PWM at their desired values.
When the 32 kHz clock is enabled in GCSR, it can be further divided by 2, 4, 6, or 8 to
generate even lower frequencies by enabling those modes in bits 0–2 of GPSCR. See
Table 2-4 for more details.
12
GCSR Setting
xxx010xx
xxx011xx
xxx110xx
xxx111xx
xxx000xx
xxx001xx
xxx100xx
xxx101xx
Main clock
Main clock / 2
Main clock / 4
Main clock / 6
Main clock / 8
Main clock / 8
32 kHz clock (possibly divided)
32 kHz clock (possibly divided);
main clock disabled via CLKIEN
output signal
Processor Clock
Table 2-1. Clock Modes
Rabbit 4000 Microprocessor User’s Manual
Main clock
Main clock / 2
Main clock / 4
Main clock / 6
Main clock / 8 (default on startup)
Main clock
32 kHz clock (possibly divided
via GPSCR)
32 kHz clock (possibly divided
via GPSCR)
Peripheral Clock