MCF5272 Datasheet, PDF (475/544 Pages) Motorola, Inc – MCF5272 ColdFire Integrated Microprocessor Users Manual

Chapter 21
IEEE 1149.1 Test Access Port (JTAG)
This chapter describes the dedicated user-accessible test logic implemented on the MCF5272. This test
logic complies fully with the IEEE 1149.1 Standard Test Access Port and Boundary Scan Architecture.
This chapter describes those items required by the standard and provides additional information specific
to the MCF5272 implementation. For internal details and sample applications, see the IEEE 1149.1
document.
21.1 Overview
Problems with testing high-density circuit boards led to development of this standard under the
sponsorship of the Test Technology Committee of IEEE and the Joint Test Action Group (JTAG). The
MCF5272 supports circuit board test strategies based on this standard.
The test logic includes a test access port (TAP) consisting a 16-state controller, an instruction register, and
three test registers (a 1-bit bypass register, a 265-bit boundary-scan register, and a 32-bit ID register). The
boundary scan register links the device’s pins into one shift register. The contents of this register can be
found at the ColdFire website at http://www.freescale.com. Test logic, implemented using static logic
design, is independent of the device system logic. The TAP includes the following dedicated signals:
• TCK—Test clock input to synchronize the test logic.
• TMS—Test mode select input (with an internal pullup resistor) that is sampled on the rising edge
of TCK to sequence the TAP controller's state machine.
• TDI—Test data input (with an internal pull-up resistor) that is sampled on the rising edge of TCK.
• TDO—three-state test data output that is actively driven in the shift-IR and shift-DR controller
states. TDO changes on the falling edge of TCK.
These signals, described in detail in Table 21-1, are enabled by negating the Freescale test mode signal
(MTMOD).
The MCF5272 implementation can do the following:
• Perform boundary scan operations to test circuit board electrical continuity
• Sample MCF5272 system pins during operation and transparently shift out the result in the
boundary scan register
• Bypass the MCF5272 for a given circuit board test by effectively reducing the boundary-scan
register to a single bit
• Disable the output drive to pins during circuit-board testing
• Drive output pins to stable levels
MCF5272 ColdFire^® Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
21-1