Datasheet

Chapter 17. Signal Descriptions 17-21
Debug Module/JTAG Signals
.
17.14 Debug Module/JTAG Signals
The MCF5307 complies with the IEEE 1149.1a JTAG testing standard. JTAG test pins are
multiplexed with background debug pins. Except for TCK, these signals are selected by the
value of MTMOD0. If MTMOD0 is high, JTAG signals are chosen; if it is low, debug
module signals are chosen. MTMOD0 should be changed only while RSTI
is asserted.
17.14.1 Test Reset/Development Serial Clock
(TRST/DSCLK)
If MTMOD0 is high, TRST is selected. TRST asynchronously resets the internal JTAG
controller to the test logic reset state, causing the JTAG instruction register to choose the
bypass instruction. When this occurs, JTAG logic is benign and does not interfere with
normal MCF5307 functionality.
Although TRST
is asynchronous, Motorola recommends that it makes an
asserted-to-negated transition only while TMS is held high. TRST
has an internal pull-up
resistor so if it is not driven low, it defaults to a logic level of 1. If TRST
is not used, it can
be tied to ground or, if TCK is clocked, to V
DD
. Tying TRST to ground places the JTAG
Table 17-17. Processor Status Signal Encodings
PST[3:0]
Definition
Hex Binary
0x0 0000 Continue execution
0x1 0001 Begin execution of an instruction
0x2 0010 Reserved
0x3 0011 Entry into user-mode
0x4 0100 Begin execution of PULSE and WDDATA instructions
0x5 0101 Begin execution of taken branch or Synch_PC
1
1
Rev. B enhancement.
0x6 0110 Reserved
0x7 0111 Begin execution of RTE instruction
0x8 1000 Begin 1-byte data transfer on DDATA
0x9 1001 Begin 2-byte data transfer on DDATA
0xA 1010 Begin 3-byte data transfer on DDATA
0xB 1011 Begin 4-byte data transfer on DDATA
0xC 1100 Exception processing
2
2
These encodings are asserted for multiple cycles.
0xD 1101 Emulator mode entry exception processing
2
0xE 1110 Processor is stopped, waiting for interrupt
2
0xF 1111 Processor is halted
2
Fr
eescale S
emiconduct
or
, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
nc...