1.1.3 Flash and OTP Power Modes
The following operating states apply to the flash and OTP memory:
•
Reset or Sleep State
This is the state after a device reset. In this state, the bank and pump are in a sleep state (lowest power).
When the flash is in the sleep state, a CPU data read or opcode fetch to the flash or OTP memory map area
will automatically initiate a change in power modes to the standby state and then to the active state. During
this transition time to the active state, the CPU will automatically be stalled. Once the transition to the active
state is completed, the CPU access will complete as normal.
•
Standby State
In this state, the bank and pump are in standby power mode state. This state uses more power then the sleep
state, but takes a shorter time to transition to the active or read state. When the flash is in the standby state,
a CPU data read or opcode fetch to the flash or OTP memory map area will automatically initiate a change in
power modes to the active state. During this transition time to the active state, the CPU will automatically be
stalled. Once the flash/OTP has reached the active state, the CPU access will complete as normal.
•
Active or Read State
In this state, the bank and pump are in active power mode state (highest power). The CPU read or fetch
access wait states to the flash/OTP memory map area is controlled by the FBANKWAIT and FOTPWAIT
registers. A prefetch mechanism called flash pipeline can also be enabled to improve fetch performance for
linear code execution.
Note
During the boot process, the Boot ROM performs a dummy read of the Code Security Module (CSM)
password locations located in the flash. This read is performed to unlock a new or erased device
that has no password stored in it so that flash programming or loading of code into CSM protected
SARAM can be performed. On devices with a password stored, this read has no effect and the CSM
remains locked (see
for information on the CSM). One effect of this read is that the flash
will transition from the sleep (reset) state to the active state.
The flash/OTP bank and pump are always in the same power mode. See
for a graphic depiction of
the available power states. You can change the current flash/OTP memory power state as follows:
•
To move to a lower power state
Change the PWR mode bits from a higher power mode to a lower power mode. This change instantaneously
moves the flash/OTP bank to the lower power state. This register should be accessed only by code running
outside the flash/OTP memory.
•
To move to a higher power state
To move from a lower power state to a higher power state, there are two options.
1. Change the FPWR register from a lower state to a higher state. This access brings the flash/OTP
memory to the higher state.
2. Access the flash or OTP memory by a read access or program opcode fetch access. This access
automatically brings the flash/OTP memory to the active state.
There is a delay when moving from a lower power state to a higher one. See
allow the flash to stabilize at the higher power mode. If any access to the flash/OTP memory occurs during this
delay the CPU automatically stalls until the delay is complete.
System Control and Interrupts
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
41
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Содержание TMS320 2806 Series
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