at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 69

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

12.5.3
12.5.4
6249D–ATARM–20-Dec-07
JTAG Signal Description
Debug Unit
There are two scan chains inside the ARM9EJ-S processor which support testing, debugging,
and programming of the Embedded ICE-RT. The scan chains are controlled by the ICE/JTAG
port.
Embedded ICE mode is selected when JTAGSEL is low. It is not possible to switch directly
between ICE and JTAG operations. A chip reset must be performed after JTAGSEL is changed.
For further details on the Embedded In-Circuit-Emulator-RT, see the ARM document:
ARM9EJ-S Technical Reference Manual (DDI 0222A).
TMS is the Test Mode Select input which controls the transitions of the test interface state
machine.
TDI is the Test Data Input line which supplies the data to the JTAG registers (Boundary Scan
Register, Instruction Register, or other data registers).
TDO is the Test Data Output line which is used to serially output the data from the JTAG regis-
ters to the equipment controlling the test. It carries the sampled values from the boundary scan
chain (or other JTAG registers) and propagates them to the next chip in the serial test circuit.
NTRST (optional in IEEE Standard 1149.1) is a Test-ReSeT input which is mandatory in ARM
cores and used to reset the debug logic. On Atmel ARM926EJ-S-based cores, NTRST is a
Power On Reset output. It is asserted on power on. If necessary, the user can also reset the
debug logic with the NTRST pin assertion during 2.5 MCK periods.
TCK is the Test ClocK input which enables the test interface. TCK is pulsed by the equipment
controlling the test and not by the tested device. It can be pulsed at any frequency. Note the
maximum JTAG clock rate on ARM926EJ-S cores is 1/6th the clock of the CPU. This gives 5.45
kHz maximum initial JTAG clock rate for an ARM9E running from the 32.768 kHz slow clock.
RTCK is the Return Test Clock. Not an IEEE Standard 1149.1 signal added for a better clock
handling by emulators. From some ICE Interface probes, this return signal can be used to syn-
chronize the TCK clock and take not care about the given ratio between the ICE Interface clock
and system clock equal to 1/6th. This signal is only available in JTAG ICE Mode and not in
boundary scan mode.
The Debug Unit provides a two-pin (DXRD and TXRD) USART that can be used for several
debug and trace purposes and offers an ideal means for in-situ programming solutions and
debug monitor communication. Moreover, the association with two peripheral data controller
channels permits packet handling of these tasks with processor time reduced to a minimum.
The Debug Unit also manages the interrupt handling of the COMMTX and COMMRX signals
that come from the ICE and that trace the activity of the Debug Communication Channel.The
Debug Unit allows blockage of access to the system through the ICE interface.
A specific register, the Debug Unit Chip ID Register, gives information about the product version
and its internal configuration.
The AT91SAM9263 Debug Unit Chip ID value is 0x0196 07A0 on 32-bit width.
For further details on the Debug Unit, see the Debug Unit section.
AT91SAM9263 Preliminary
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