CC2540T Datasheet, PDF (23/37 Pages) Texas Instruments – Extended Industrial Temperature Bluetooth Smart Wireless MCU

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CC2540T
SWRS172A – JULY 2014 – REVISED NOVEMBER 2015
The memory arbiter is at the heart of the system, as it connects the CPU and DMA controller with the
physical memories and all peripherals through the SFR bus. The memory arbiter has four memory-access
points, access of which can map to one of three physical memories: an SRAM, flash memory, with
XREG/SFR registers. It is responsible for performing arbitration and sequencing between simultaneous
memory accesses to the same physical memory.
The SFR bus is drawn conceptually in Figure 5-1 as a common bus that connects all hardware
peripherals to the memory arbiter. The SFR bus in the block diagram also provides access to the radio
registers in the radio register bank, even though these are indeed mapped into XDATA memory space.
The 8-KB SRAM maps to the DATA memory space and to parts of the XDATA memory spaces. The
SRAM is an ultralow-power SRAM that retains its contents even when the digital part is powered off
(power modes 2 and 3).
The 256-KB flash block provides in-circuit programmable non-volatile program memory for the device,
and maps into the CODE and XDATA memory spaces.
5.3.2 Peripherals
Writing to the flash block is performed through a flash controller that allows page-wise erasure and
4-bytewise programming. See the User's Guide (SWRU191) for details on the flash controller.
A versatile five-channel DMA controller is available in the system, accesses memory using the XDATA
memory space, and thus has access to all physical memories. Each channel (trigger, priority, transfer
mode, addressing mode, source and destination pointers, and transfer count) is configured with DMA
descriptors that can be located anywhere in memory. Many of the hardware peripherals (AES core, flash
controller, USARTs, timers, ADC interface, and so forth) can be used with the DMA controller for efficient
operation by performing data transfers between a single SFR or XREG address and flash/SRAM.
Each CC2540T contains a unique 48-bit IEEE address that can be used as the public device address for a
Bluetooth device. Designers are free to use this address, or provide their own, as described in the
Bluetooth specification.
The interrupt controller services a total of 18 interrupt sources, divided into six interrupt groups, each of
which is associated with one of four interrupt priorities. I/O and sleep timer interrupt requests are serviced
even if the device is in a sleep mode (power modes 1 and 2) by bringing the CC2540T back to the active
mode.
The debug interface implements a proprietary two-wire serial interface that is used for in-circuit
debugging. Through this debug interface, it is possible to erase or program the entire flash memory,
control which oscillators are enabled, stop and start execution of the user program, execute instructions
on the 8051 core, set code breakpoints, and single-step through instructions in the code. Using these
techniques, it is possible to perform in-circuit debugging and external flash programming elegantly.
The I/O controller is responsible for all general-purpose I/O pins. The CPU can configure whether
peripheral modules control certain pins or whether they are under software control, and if so, whether
each pin is configured as an input or output and if a pullup or pulldown resistor in the pad is connected.
Each peripheral that connects to the I/O pins can choose between two different I/O pin locations to ensure
flexibility in various applications.
The sleep timer is an ultralow-power timer that can either use an external 32.768-kHz crystal oscillator or
an internal 32.753-kHz RC oscillator. The sleep timer runs continuously in all operating modes except
power mode 3. Typical applications of this timer are as a real-time counter or as a wake-up timer to get
out of power modes 1 or 2.
A built-in watchdog timer allows the CC2540T to reset itself if the firmware hangs. When enabled by
software, the watchdog timer must be cleared periodically; otherwise, it resets the device when it times
out.
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