at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 60

• Manufacturer Part Number: at91sam9g20-cu
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

12.5.4
12.5.5
12.5.5.1
60
AT91SAM9G20 Preliminary
Debug Unit
IEEE 1149.1 JTAG Boundary Scan
JTAG Boundary-scan Register
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 AT91SAM9G20 Debug Unit Chip ID value is 0x0199 05A1 on 32-bit width.
For further details on the Debug Unit, see the Debug Unit section.
IEEE 1149.1 JTAG Boundary Scan allows pin-level access independent of the device packaging
technology.
IEEE 1149.1 JTAG Boundary Scan is enabled when JTAGSEL is high. The SAMPLE, EXTEST
and BYPASS functions are implemented. In ICE debug mode, the ARM processor responds
with a non-JTAG chip ID that identifies the processor to the ICE system. This is not IEEE 1149.1
JTAG-compliant.
It is not possible to switch directly between JTAG and ICE operations. A chip reset must be per-
formed after JTAGSEL is changed.
A Boundary-scan Descriptor Language (BSDL) file is provided to set up test.
The Boundary-scan Register (BSR) contains 308 bits that correspond to active pins and associ-
ated control signals.
Each AT91SAM9G20 input/output pin corresponds to a 3-bit register in the BSR. The OUTPUT
bit contains data that can be forced on the pad. The INPUT bit facilitates the observability of data
applied to the pad. The CONTROL bit selects the direction of the pad.
Table 12-2.
Bit Number
307
306
305
304
303
302
301
300
299
298
AT91SAM9G20 JTAG Boundary Scan Register
Pin Name
A10
A11
A12
A0
A1
Pin Type
IN/OUT
IN/OUT
IN/OUT
IN/OUT
IN/OUT
Associated BSR Cells
INPUT/OUTPUT
INPUT/OUTPUT
INPUT/OUTPUT
INPUT/OUTPUT
INPUT/OUTPUT
CONTROL
CONTROL
CONTROL
CONTROL
CONTROL
6384B–ATARM–15-Dec-08