CP3BT23_14 Datasheet, PDF (120/324 Pages) Texas Instruments – CP3BT23 Reprogrammable Connectivity Processor with Bluetooth and Dual CAN Interfaces

CP3BT23
SNOSCX3A – JULY 2013 – REVISED JANUARY 2014
www.ti.com
17 Random Number Generator (RNG)
The RNG unit is a hardware “true random” number generator. When enabled, this unit provides up to 800
random bits per second. The bits are available for reading from a 16-bit register.
The RNG unit includes two oscillators which operate independently of the System Clock:
• Fast Oscillator — a 24 MHz oscillator which drives a linear feedback shift register (LFSR).
• Slow Oscillator— an unstable oscillator which drives a flip-flop for sampling the pseudorandom
bitstream from the LFSR. This oscillator operates at approximately 115 kHz, but it does not have a
fixed frequency.
By sampling the pseudorandom bitstream at random intervals, a random bitstream is synthesized. This
bitstream is clocked into a 16-bit shift register. A programmable clock divider generates the clock signal for
the shift register from the System Clock.
When a new 16-bit word of random data is available, it is loaded into the RNGD register. If enabled, an
interrupt request (IRQ3) is asserted when the word is available for reading. When software reads the
RNGD register, the register is cleared and the interrupt request is deasserted.
The RNGCST register provides control and status bits for the RNG module:
• RNG Enable — enables or disables the RNG oscillators.
• Interrupt Mask — enables or disables the interrupt when a new word of random data becomes
available.
• Data Valid — indicates whether a new word is available.
17.1 FREEZE
The RNG module provides support for an In-System Emulator by means of a special FREEZE input.
When FREEZE is asserted, the automatic clear-on-read function of the RNDGD register is disabled.
Figure 17-1. RNG Module Block Diagram
17.2 Random Number Generator Register Set
Name
RNGCST
RNGD
RNGDIVH
RNGDIVL
Table 17-1. RNG Registers
Address
FF F280h
FF F282h
FF F284h
FF F286h
Description
RNG Control and Status Register
RNG Data Register
RNGDIVH FF F284h RNG Divisor Register High
RNGDIVL FF F286h RNG Divisor Register Low
120 Random Number Generator (RNG)
Submit Documentation Feedback
Product Folder Links: CP3BT23
Copyright © 2013–2014, Texas Instruments Incorporated