
EM358x
Rev. 0.4
55
Note:
Disabling all debug functionality prevents external debug tools from operating, including flash programming
and high-level debug tools.
Disabling the entire SWJ debugger interface is accomplished by setting the GPIO_DEBUGDIS bit in the
GPIO_DBGCFG register and not having GPIO PC4 configured in SWDIO mode. In this configuration all
debugger-related pins (PC0, PC2, PC3, PC4) behave as standard GPIOs.
Disabling only the JTAG debugger interface is accomplished by setting the GPIO_DEBUGDIS bit and configuring
PC4 in SWDIO mode. When GPIO_DEBUGDIS is set and GPIO PC4 is in SWDIO mode, JTAG debugger-related
pins (PC0, PC2, PC3) behave as standard GPIOs. Note that allowing the PC4 GPIO to operate as SWDIO does
not affect the internal debug state of the chip.
If the SWJ debugger interface is already active (in either mode), the bit GPIO_DEBUGDIS cannot be set. When
GPIO_DEBUGDIS is set, the SWJ debugger interface can be reclaimed by activating the SWJ while the EM358x
is held in reset. If the SWJ debugger interface is forced active in this manner, the bit GPIO_FORCEDBG is set in
the GPIO_DBGSTAT register. The SWJ debugger interface is defined as active when the CDBGPWRUPREQ
signal, a bit in the debug port’s CRTL/STAT register in the SWJ, is set high by an external debug tool.
If the SWJ debugger interface is active, and switched into Serial Wire mode (by the external debugger), then the
JTAG only pins (PC0, PC2, PC3) behave as standard GPIOs. The use of SWDIO mode for GPIO PC4 allows
reclaiming the JTAG only pins when an external debugger is not used.
7.4 Reset
A full chip reset is one due to power on (low or high voltage), the nRESET pin, the watchdog, or the
SYSRESETREQ bit. A full chip reset affects the GPIO configuration as follows:
The GPIO_PxCFGH/L configurations of all pins are configured as floating inputs.
The GPIO_EXTREGEN bit is set in the GPIO_DBGCFG register, which overrides the normal configuration for
PA7.
The GPIO_DEBUGDIS bit in the GPIO_DBGCFG register is cleared, allowing Serial Wire/JTAG access to
override the normal configuration of PC0, PC2, PC3, and PC4.
7.5 Boot Configuration
nBOOTMODE is a special alternate function of PA5 that is active only during a pin reset (nRESET) or a power-
on-reset of the always-powered domain (POR HV). If nBOOTMODE is asserted (pulled or driven low) when
coming out of reset, the processor starts executing an embedded serial-link-only monitor instead of its normal
program.
While in reset and during the subsequent power-on-reset startup delay (512 OSCHF clocks), PA5 is automatically
configured as an input with a pull-up resistor. At the end of this time, the EM358x samples nBOOTMODE: a high
level selects normal boot mode, and a low level selects the embedded monitor. Figure 7-2 shows the timing
parameters for invoking monitor mode from a pin (nRESET) reset. Because OSCHF is running uncalibrated
during the reset sequence, the time for 512 OSCHF clocks may vary as indicated.
Summary of Contents for EMBER EM358 series
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