System Register Block
UG0331 User Guide Revision 15.0
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22
System Register Block
The System Register (SYSREG) block is an array of system-level registers that contain user
configuration information used to configure the microcontroller subsystem (MSS). The contents of these
registers are initially set based on the information entered using the MSS configurator in the Libero
software. The power-up initialized state of these registers, as well as write protection bits are controlled
by flash configuration bits. The configuration bits are set during device programming.
The SYSREG block is connected to the AHB bus matrix and can be accessed by all bus masters. Write
access to these registers provides the capability to modify the initialized SYSREG block register contents
by the user application. There are seven types of System Registers as described in
which provide different levels of read/write access by bus masters.
22.0.1
SYSREG Block Register Write Protection
Each SYSREG block register has dedicated write protect bits to control write access from bus masters.
Write protect bits are flash configuration bits that are set based on user inputs to the MSS configurator.
These bits are defined during the device design phase and can only be modified by reprogramming the
device. Users have the ability to set protection levels for the entire register, independent fields within
each register, or individual bits within each register.
22.0.1.1 Register Write Protect
One Register Write Protect bit is used to write protect entire register contents as shown in the following
figure. On power-up, the register contents are initialized based on the flash configuration bits set from the
MSS configurator. If the Register Write Protect bit is set in the MSS configurator, the initialized value of
the entire register cannot be modified by the user application. If the Register Write Protect bit is not set,
the contents of the register can be modified by any bus master. Register Write Protect bits can only be
modified by reprogramming the FPGA and is therefore protected by the standard FPGA programming
security features.
Figure 309 •
Register Write Protect
32 Flash Bits for Initialization
32-Bit Control Register
Write
Protect BIt
On Power-Up, Initialize
DFFs with Flash Bits
The write protect bit keeps bus masters from changing the contents of
the Control register.