Si1000/1/2/3/4/5
1.2. CIP-51™ Microcontroller Core
1.2.1. Fully 8051 Compatible
The Si1000/1/2/3/4/5 family utilizes Silicon Labs' proprietary CIP-51 microcontroller core. The CIP-51 is
fully compatible with the MCS-51™ instruction set; standard 803x/805x assemblers and compilers can be
used to develop software. The CIP-51 core offers all the peripherals included with a standard 8052.
1.2.2. Improved Throughput
The CIP-51 employs a pipelined architecture that greatly increases its instruction throughput over the stan-
dard 8051 architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system
clock cycles to execute with a maximum system clock of 12-to-24 MHz. By contrast, the CIP-51 core exe-
cutes 70% of its instructions in one or two system clock cycles, with only four instructions taking more than
four system clock cycles.
The CIP-51 has a total of 109 instructions. The table below shows the total number of instructions that
require each execution time.
Clocks to Execute
1
2
2/3
5
3
3/4
7
4
3
4/5
1
5
2
8
1
Number of Instructions
26
50
14
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS.
1.2.3. Additional Features
The Si1000/1/2/3/4/5 SoC family includes several key enhancements to the CIP-51 core and peripherals to
improve performance and ease of use in end applications.
The extended interrupt handler provides multiple interrupt sources into the CIP-51, allowing numerous
analog and digital peripherals to interrupt the controller. An interrupt driven system requires less interven-
tion by the MCU, giving it more effective throughput. The extra interrupt sources are very useful when
building multi-tasking, real-time systems.
Eight reset sources are available: power-on reset circuitry (POR), an on-chip V
monitor (forces reset
DD
when power supply voltage drops below safe levels), a watchdog timer, a Missing Clock Detector, SmaRT-
Clock oscillator fail or alarm, a voltage level detection from Comparator0, a forced software reset, an exter-
nal reset pin, and an illegal Flash access protection circuit. Each reset source except for the POR, Reset
Input Pin, or Flash error may be disabled by the user in software. The WDT may be permanently disabled
in software after a power-on reset during MCU initialization.
The internal oscillator factory is calibrated to 24.5 MHz and is accurate to ±2% over the full temperature
and supply range. The internal oscillator period can also be adjusted by user firmware. An additional
20 MHz low power oscillator is also available which facilitates low-power operation. An external oscillator
drive circuit is included, allowing an external crystal, ceramic resonator, capacitor, RC, or CMOS clock
source to generate the system clock. If desired, the system clock source may be switched between both
internal and external oscillator circuits. An external oscillator can also be extremely useful in low power
applications, allowing the MCU to run from a slow (power saving) source, while periodically switching to
the fast (up to 25 MHz) internal oscillator as needed.
Rev. 1.0
21
SILICON [ SILICON ]
