EM357-RTR datasheet(25/240 Pages) ETC2

25 / 240 page

EM351 / EM357

3-2

120-035X-000D

Preliminary

The EM35x integrates an ARM® CortexTM-M3 microprocessor, revision r1p1. This industry-leading core provides

32 bit performance and is very power efficient. It has excellent code density using the ARM® Thumb-2

instruction set. The processor can be operated at 12 MHz or 24 MHz when using the high-frequency crystal

oscillator, or at 6 MHz or 12 MHz when using the high-frequency internal RC oscillator.

The EM351 has 128 kB of flash memory and the EM357 has 192 kB of flash memory. Both chips have 12 kB of

RAM on-chip, and the ARM configurable memory protection unit (MPU).

The EM35x implements both the ARM Serial Wire and JTAG debug interfaces. These interfaces provide real

time, non-intrusive programming and debugging capabilities. Serial Wire and JTAG provide the same

functionality, but are mutually exclusive. The Serial Wire interface uses two pins; the JTAG interface uses

five. Serial Wire is preferred, since it uses fewer pins.

The EM35x contains 24 GPIO pins shared with other peripheral or alternate functions. Because of flexible

routing within the EM35x, external devices can use the alternate functions on a variety of different GPIOs. The

integrated serial controller SC1 can be configured for SPI (master or slave), TWI (master-only), or UART

operation, and the serial controller SC2 can be configured for SPI (master or slave) or TWI (master-only)

operation.

The EM35x has a general purpose ADC which can sample analog signals from six GPIO pins in single-ended or

differential modes. It can also sample the 1.8 V regulated supply VDD_PADSA, the voltage reference VREF, and

GND. The ADC has two selectable voltage ranges: 0 V to 1.2 V (normal) and 0.1 V to 0.1 V below the high

voltage supply (high). The ADC has a DMA mode to capture samples and automatically transfer them into RAM.

The integrated voltage reference for the ADC, VREF, can be made available to external circuitry. An external

voltage reference can also be driven into the ADC. The regulator input voltage, VDD_PADS, cannot be

measured using the general purpose ADC, but it can be measured through Ember software.

The EM35x contains four oscillators: a high-frequency 24 MHz external crystal oscillator, a high-frequency

12 MHz internal RC oscillator, an optional low-frequency 32.768 kHz external crystal oscillator, and a low-

frequency 10 kHz internal RC oscillator.

The EM35x has an ultra low power, deep sleep state with a choice of clocking modes. The sleep timer can be

clocked with either the external 32.768 kHz crystal oscillator or with a 1 kHz clock derived from the internal

10 kHz RC oscillator. Alternatively, all clocks can be disabled for the lowest power mode. In the lowest power

mode, only external events on GPIO pins will wake up the chip. The EM35x has a fast startup time (typically

110 µs) from deep sleep to the execution of the first ARM® CortexTM-M3 instruction.

The EM35x contains three power domains. The always-on high voltage supply powers the GPIO pads and

critical chip functions. Regulated low voltage supplies power the rest of the chip. The low voltage supplies are

disabled during deep sleep to reduce power consumption. Integrated voltage regulators generate regulated

1.25 V and 1.8 V voltages from an unregulated supply voltage. The 1.8 V regulator output is decoupled and

routed externally to supply analog blocks, RAM, and flash memories. The 1.25 V regulator output is decoupled

externally and supplies the core logic.

Note:

The EM35x is not pin-compatible with Ember’s previous generation chip, the EM250, except for the RF

section of the chip. Pins 1-11 and 45-48 are compatible, to ease migration to the EM35x.

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