AN2074 Freescale Semiconductor / Motorola, AN2074 Datasheet - Page 3

• Manufacturer Part Number: AN2074
• Description: DSP56300 JTAG Examples
• Manufacturer: Freescale Semiconductor / Motorola

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1.1 JTAG Pins
1.2 TAP Controller
The TAP is the external interface for the internal test circuitry specified by IEEE 1149.1. It consists of the
following:
IEEE 1149.1 requires a minimum of four signals to support the TAP. The DSP56300 family supports these
signals and the optional reset signal. The supported signals include the following:
The TAP controller is a 16-state machine that manages the functions of the test environment and perform
the instruction and data transfers. Figure 3 shows the 16-state TAP controller state machine. The state
machine performs three basic actions:
The TAP changes state based on the level of
edge of
TCK
technique prevents the development of a race condition in the TAP.
Test Access Port
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, while data is transferred out through
TCK
Five dedicated signal pins
16-state TAP controller
Instruction Register
Four Data Registers, including:
— Bypass Register (BR)
— Device ID Register (IDR)
— Boundary-Scan Register (BSR)
— OnCE Control Register (OCR), used to access the other OnCE registers
Test Clock (
data and instructions into the device and to strobe data out of the device.
Test Mode Select (
processing state.
Test Data Input (
TDI
Test Data Output (
changes on the falling edge of
Test Reset (
TRST
Do nothing. Test-Logic-Reset or Run-Test/Idle state
Load a new instruction. Instruction Register scan cycle
Load new data into a selected data register. Data Register scan cycle
is sampled on the rising edge of
. Instructions and data are transferred in through
is asynchronous to
TRST
TCK
Freescale Semiconductor, Inc.
). This input provides a clock signal used to sample the
TDI
TMS
). This input is asserted low to reset the TAP circuitry to a known initial state.
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TDO
TMS
). This input is used to transfer instructions and data serially into the device.
is sampled on the rising edge of
). This output is used to transfer data out of the device serially.
). This input is used to change the TAP controller state machine to the next
TCK
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DSP56300 JTAG Examples
TCK
and has an internal pull-up resistor.
TDO
.
TMS
TCK
, which changes on the falling edge of
. Transitions from one state to another occur on the rising
and has an internal pull-up resistor.
TDI
TCK
, which is sampled on the rising edge of
and has an internal pull-up resistor.
TMS
TCK
signal and to strobe
TAP Controller
. This sampling
TDO
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