XC2200 Derivatives
System Units (Vol. 1 of 2)
System Control Unit (SCU)
User’s Manual
6-151
V2.1, 2008-08
SCU, V1.13
6.6
Global State Controller (GSC)
Mode Control for the system peripherals provides besides power saving modes and the
clock management an additional opportunity for configuring the system to the application
needs.
Mode Control is described in detail in this chapter and is implemented by the Global
State Controller (GSC). The GSC enables the user to configure one operating mode in
a fast and easy way, reacting fast and explicit to needs of an application.
Feature Overview
The following issues are handled by the GSC:
•
Control of peripheral clock operation
•
Suspend control for debugging
•
Arbitration between the different request sources
According to the requests coming from the OCDS, the SWD pre-warning detection or
other blocks, the GSC does an internal prioritization. The result is forwarded as
command request broadcast to all peripherals. The GSC internal prioritization scheme
for the implemented request sources is shown in
6.6.1
GSC Control Flow
The sequence begins when at least one request source asserts its trigger in order to
request a mode change in the SoC. If several requests are pending there is an arbitration
mechanism that treats this issue. Request triggers are not stored by the GSC, therefore
a trigger source has to assert its trigger until the trigger is no longer valid or needed.
A request trigger is kept asserted as long as either the request is still pending or the
resulting command of the request was entered and acknowledged by the system. The
communication of the GSC and the peripherals is based on commands. Three different
commands are defined resulting in three modes:
•
Wake-up command: requests Normal Mode
•
Clock-off command: requests Stop Mode
•
Debug command: requests Suspend Mode
The specific behavior in these three modes is defined for each peripheral in its module
register mod_KSCCFG.
6.6.1.1
Request Source Arbitration
The highest priority for the arbitration is zero (see
Each system clock cycle a new arbitration round is started. The winner of an arbitration
round requests the next command towards the SoC. Please note that winning an
arbitration does not lead automatically to a new command raised. Only if currently no
command is broadcast in the SoC a new command can be generated and broadcast. If