Datasheet

Table Of Contents
JTAG/OnCE
56F805 Technical Data, Rev. 16
Freescale Semiconductor 19
2.14 JTAG/OnCE
Part 3 Specifications
3.1 General Characteristics
The 56F805 is fabricated in high-density CMOS with 5V-tolerant TTL-compatible digital inputs. The term
“5V-tolerant” refers to the capability of an I/O pin, built on a 3.3V-compatible process technology, to
withstand a voltage up to 5.5V without damaging the device. Many systems have a mixture of devices
designed for 3.3V and 5V power supplies. In such systems, a bus may carry both 3.3V and 5V-compatible
I/O voltage levels (a standard 3.3V I/O is designed to receive a maximum voltage of 3.3V ± 10% during
Table 2-18 JTAG/On-Chip Emulation (OnCE) Signals
No. of
Pins
Signal
Name
Signal
Type
State During
Reset
Signal Description
1 TCK Input
(Schmitt)
Input, pulled
low internally
Test Clock Input—This input pin provides a gated clock to
synchronize the test logic and shift serial data to the JTAG/OnCE
port. The pin is connected internally to a pull-down resistor.
1 TMS Input
(Schmitt)
Input, pulled
high internally
Test Mode Select Input—This input pin is used to sequence the
JTAG TAP controller’s state machine. It is sampled on the rising
edge of TCK and has an on-chip pull-up resistor.
Note: Always tie the TMS pin to V
DD
through a 2.2K resistor.
1 TDI Input
(Schmitt)
Input, pulled
high internally
Test Data Input—This input pin provides a serial input data stream
to the JTAG/OnCE port. It is sampled on the rising edge of TCK and
has an on-chip pull-up resistor.
1 TDO Output Tri-stated Test Data Output—This tri-statable output pin provides a serial
output data stream from the JTAG/OnCE port. It is driven in the
Shift-IR and Shift-DR controller states, and changes on the falling
edge of TCK.
1 TRST
Input
(Schmitt)
Input, pulled
high internally
Test Reset—As an input, a low signal on this pin provides a reset
signal to the JTAG TAP controller. To ensure complete hardware
reset, TRST
should be asserted at power-up and whenever RESET
is asserted. The only exception occurs in a debugging environment
when a hardware device reset is required and it is necessary not to
reset the OnCE/JTAG module. In this case, assert RESET
, but do
not assert TRST
.
Note: For normal operation, connect TRST directly to V
SS
. If the design
is to be used in a debugging environment, TRST
may be tied to V
SS
through a 1K resistor.
1 DE
Output Output Debug Event—DE provides a low pulse on recognized debug
events.