MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
24-4
Freescale Semiconductor
The boundary scan register is enabled for serial access between TDI and TDO when the EXTEST,
SAMPLE or SAMPLE/PRELOAD instructions are active. The single-bit bypass register shift stage is
enabled for serial access between TDI and TDO when the HIGHZ, CLAMP or reserved instructions are
active. The functionality of each test mode is explained in more detail in
24.1.4.3
Bypass Mode
When no test operation is required, the BYPASS instruction can be loaded to place the JTAGC into bypass
mode. While in bypass mode, the single-bit bypass shift register is used to provide a minimum-length
serial path to shift data between TDI and TDO.
24.1.4.4
TAP Sharing Mode
On the MPC5553/MPC5554, there are four selectable auxiliary TAP controllers that share the TAP with
the JTAGC. Selectable TAP controllers include the Nexus port controller (NPC), e200 OnCE, eTPU
Nexus, and eDMA Nexus. The instructions required to grant ownership of the TAP to the auxiliary TAP
controllers are ACCESS_AUX_TAP_NPC, ACCESS_AUX_TAP_ONCE,
ACCESS_AUX_TAP_eTPUN3, and ACCESS_AUX_TAP_DMAN3. Instruction opcodes for each
instruction are shown in
.
When the access instruction for an auxiliary TAP is loaded, control of the JTAG pins is transferred to the
selected TAP controller. Any data input via TDI and TMS is passed to the selected TAP controller, and any
TDO output from the selected TAP controller is sent back to the JTAGC to be output on the pins. The
JTAGC regains control of the JTAG port during the UPDATE-DR state if the PAUSE-DR state was
entered. Auxiliary TAP controllers are held in RUN-TEST/IDLE while they are inactive.
For more information on the TAP controllers see
Chapter 25, “Nexus Development Interface
24.2
External Signal Description
24.2.1
Overview
The JTAGC consists of five signals that connect to off-chip development tools and allow access to test
support functions. The JTAGC signals are outlined in
.
Table 24-1. JTAG Signal Properties
Name
I/O
Function
Reset State
Pull
1
1
The pull is not implemented in this module. Pull-up/pull-down devices are implemented in the pads.
TCK
I
Test Clock
—
Down
TDI
I
Test Data In
—
Up
TDO
O
Test Data Out
High Z
2
2
TDO output buffer enable is negated when JTAGC is not in the Shift-IR or Shift-DR states. A weak
pull-down may be implemented on TDO.
Down
TMS
I
Test Mode Select
—
Up
JCOMP
I
JTAG Compliancy
—
Down
Summary of Contents for MPC5553
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