LM3S8970 Luminary Micro, Inc, LM3S8970 Datasheet - Page 33

• Manufacturer Part Number: LM3S8970
• Description: Lm3s8970 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

1.4.4.2
1.4.4.3
1.4.5
1.4.5.1
1.4.5.2
July 25, 2008
The Stellaris
an individual GPIO port. The GPIO module is FiRM-compliant (compliant to the ARM Foundation
IP for Real-Time Microcontrollers specification) and supports 17-46 programmable input/output pins.
The number of GPIOs available depends on the peripherals being used (see “Signal Tables” on page
463 for the signals available to each GPIO pin).
The GPIO module features programmable interrupt generation as either edge-triggered or
level-sensitive on all pins, programmable control for GPIO pad configuration, and bit masking in
both read and write operations through address lines. Pins configured as digital inputs are
Schmitt-triggered.
Four Programmable Timers (see page 203)
Programmable timers can be used to count or time external events that drive the Timer input pins.
The Stellaris
block provides two 16-bit timers/counters that can be configured to operate independently as timers
or event counters, or configured to operate as one 32-bit timer or one 32-bit Real-Time Clock (RTC).
When configured in 32-bit mode, a timer can run as a Real-Time Clock (RTC), one-shot timer or
periodic timer. When in 16-bit mode, a timer can run as a one-shot timer or periodic timer, and can
extend its precision by using an 8-bit prescaler. A 16-bit timer can also be configured for event
capture or Pulse Width Modulation (PWM) generation.
Watchdog Timer (see page 239)
A watchdog timer can generate nonmaskable interrupts (NMIs) or a reset when a time-out value is
reached. The watchdog timer is used to regain control when a system has failed due to a software
error or to the failure of an external device to respond in the expected way.
The Stellaris
register, interrupt generation logic, and a locking register.
The Watchdog Timer can be configured to generate an interrupt to the controller on its first time-out,
and to generate a reset signal on its second time-out. Once the Watchdog Timer has been configured,
the lock register can be written to prevent the timer configuration from being inadvertently altered.
Memory Peripherals
The LM3S8970 controller offers both single-cycle SRAM and single-cycle Flash memory.
SRAM (see page 138)
The LM3S8970 static random access memory (SRAM) controller supports 64 KB SRAM. The internal
SRAM of the Stellaris
reduce the number of time-consuming read-modify-write (RMW) operations, ARM has introduced
bit-banding technology in the new Cortex-M3 processor. With a bit-band-enabled processor, certain
regions in the memory map (SRAM and peripheral space) can use address aliases to access
individual bits in a single, atomic operation.
Flash (see page 139)
The LM3S8970 Flash controller supports 256 KB of flash memory. The flash is organized as a set
of 1-KB blocks that can be individually erased. Erasing a block causes the entire contents of the
block to be reset to all 1s. These blocks are paired into a set of 2-KB blocks that can be individually
protected. The blocks can be marked as read-only or execute-only, providing different levels of code
protection. Read-only blocks cannot be erased or programmed, protecting the contents of those
blocks from being modified. Execute-only blocks cannot be erased or programmed, and can only
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GPIO module is comprised of seven physical GPIO blocks, each corresponding to
General-Purpose Timer Module (GPTM) contains four GPTM blocks. Each GPTM
Watchdog Timer module consists of a 32-bit down counter, a programmable load
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devices is located at offset 0x0000.0000 of the device memory map. To
Preliminary
LM3S8970 Microcontroller
33