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SAM3S8/SD8 Summary
Notes: 1. If PB12 is used as PIO input in user applications, a low level must be ensured at startup to prevent Flash erase before the
user application sets PB12 into PIO mode,
2. In the product Datasheet Refer to: “Slow Clock Generator” of the “Supply Controller” section.
3. In the product Datasheet Refer to: “3 to 20 MHZ Crystal Oscillator” information in the “PMC” section.
6.2.1 Serial Wire JTAG Debug Port (SWJ-DP) Pins
The SWJ-DP pins are TCK/SWCLK, TMS/SWDIO, TDO/SWO, TDI and commonly provided on
a standard 20-pin JTAG connector defined by ARM. For more details about voltage reference
and reset state, refer to Table 3-1 on page 5.
At startup, SWJ-DP pins are configured in SWJ-DP mode to allow connection with debugging
probe. Please refer to the “Debug and Test” Section of the product datasheet.
SWJ-DP pins can be used as standard I/Os to provide users more general input/output pins
when the debug port is not needed in the end application. Mode selection between SWJ-DP
mode (System IO mode) and general IO mode is performed through the AHB Matrix Special
Function Registers (MATRIX_SFR). Configuration of the pad for pull-up, triggers, debouncing
and glitch filters is possible regardless of the mode.
The JTAGSEL pin is used to select the JTAG boundary scan when asserted at a high level. It
integrates a permanent pull-down resistor of about 15 kΩ to GND, so that it can be left uncon-
nected for normal operations.
By default, the JTAG Debug Port is active. If the debugger host wants to switch to the Serial
Wire Debug Port, it must provide a dedicated JTAG sequence on TMS/SWDIO and
TCK/SWCLK which disables the JTAG-DP and enables the SW-DP. When the Serial Wire
Debug Port is active, TDO/TRACESWO can be used for trace.
The asynchronous TRACE output (TRACESWO) is multiplexed with TDO. So the asynchronous
trace can only be used with SW-DP, not JTAG-DP. For more information about SW-DP and
JTAG-DP switching, please refer to the “Debug and Test” Section.
Table 6-1. System I/O Configuration Pin List.
SYSTEM_IO
bit number
Default function
after reset Other function
Constraints for
normal start Configuration
12 ERASE PB12 Low Level at startup
(1)
In Matrix User Interface Registers
(Refer to the System I/O
Configuration Register in the “Bus
Matrix” section of the datasheet.)
10 DDM PB10 -
11 DDP PB11 -
7 TCK/SWCLK PB7 -
6 TMS/SWDIO PB6 -
5 TDO/TRACESWO PB5 -
4 TDI PB4 -
- PA7 XIN32 -
See footnote
(2)
below
- PA8 XOUT32 -
- PB9 XIN -
See footnote
(3)
below
- PB8 XOUT -
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SAM3S8/SD8 Summary
6.3 Test Pin
The TST pin is used for JTAG Boundary Scan Manufacturing Test or Fast Flash programming
mode of the SAM3S8/SD8 series. The TST pin integrates a permanent pull-down resistor of
about 15 kΩ to GND, so that it can be left unconnected for normal operations. To enter fast pro-
gramming mode, see the Fast Flash Programming Interface (FFPI) section. For more on the
manufacturing and test mode, refer to the “Debug and Test” section of the product datasheet.
6.4 NRST Pin
The NRST pin is bidirectional. It is handled by the on-chip reset controller and can be driven low
to provide a reset signal to the external components or asserted low externally to reset the
microcontroller. It will reset the Core and the peripherals except the Backup region (RTC, RTT
and Supply Controller). There is no constraint on the length of the reset pulse and the reset con-
troller can guarantee a minimum pulse length. The NRST pin integrates a permanent pull-up
resistor to VDDIO of about 100 kΩ. By default, the NRST pin is configured as an input.
6.5 ERASE Pin
The ERASE pin is used to reinitialize the Flash content (and some of its NVM bits) to an erased
state (all bits read as logic level 1). It integrates a pull-down resistor of about 100 kΩ to GND, so
that it can be left unconnected for normal operations.
This pin is debounced by SCLK to improve the glitch tolerance. When the ERASE pin is tied high
during less than 100 ms, it is not taken into account. The pin must be tied high during more than
220 ms to perform a Flash erase operation.
The ERASE pin is a system I/O pin and can be used as a standard I/O. At startup, the ERASE
pin is not configured as a PIO pin. If the ERASE pin is used as a standard I/O, startup level of
this pin must be low to prevent unwanted erasing. Refer to Section 10.17 “Peripheral Signal Mul-
tiplexing on I/O Lines” on page 40. Also, if the ERASE pin is used as a standard I/O output,
asserting the pin to low does not erase the Flash.
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11090BS–ATARM–22-Oct-13
SAM3S8/SD8 Summary
7. Processor and Architecture
7.1 ARM Cortex-M3 Processor
Version 2.0
Thumb-2 (ISA) subset consisting of all base Thumb-2 instructions, 16-bit and 32-bit.
Harvard processor architecture enabling simultaneous instruction fetch with data load/store.
Three-stage pipeline.
Single cycle 32-bit multiply.
Hardware divide.
Thumb and Debug states.
Handler and Thread modes.
Low latency ISR entry and exit.
7.2 APB/AHB bridge
The SAM3S8/SD8 embeds One Peripheral bridge:
The peripherals of the bridge are clocked by MCK.
7.3 Matrix Masters
The Bus Matrix of the SAM3S8/SD8 manages 4 masters, which means that each master can
perform an access concurrently with others, to an available slave.
Each master has its own decoder, which is defined specifically for each master. In order to sim-
plify the addressing, all the masters have the same decodings.
7.4 Matrix Slaves
The Bus Matrix of the SAM3S8/SD8 manages 5 slaves. Each slave has its own arbiter, allowing
a different arbitration per slave.
Table 7-1. List of Bus Matrix Masters
Master 0 Cortex-M3 Instruction/Data
Master 1 Cortex-M3 System
Master 2 Peripheral DMA Controller (PDC)
Master 3 CRC Calculation Unit
Table 7-2. List of Bus Matrix Slaves
Slave 0 Internal SRAM
Slave 1 Internal ROM
Slave 2 Internal Flash
Slave 3 External Bus Interface
Slave 4 Peripheral Bridge

ATSAM3SD8BA-MU

Mfr. #:
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Microchip Technology / Atmel
Description:
ARM Microcontrollers - MCU QFN,Grn, IT, MRL A
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