PXD20RM Datasheet, PDF (1129/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

Table 30-12. Nexus Client JTAG Instructions
Instruction
Description
NEXUS2_ACCESS
Opcode for e200z4d OnCE Nexus ENABLE instruction
(10-bits)
BYPASS
Opcode for the e200z4d OnCE BYPASS instruction
(10-bits)
1 _{See the e200z4d core reference manual for a complete list of available OnCE instructions.}
Opcode
0x7C
0x7F
30.7.3 Configuring the NDI for Nexus Messaging
The NDI is placed in disabled mode upon exit of reset. If message transmission via the auxiliary port is
desired, a write to the port configuration register (PCR) located in the NPC is then required to enable the
NDI and select the mode of operation. Asserting MCKO_EN in the PCR places the NDI in enabled mode
and enables MCKO. The frequency of MCKO is selected by writing the MCKO_DIV field. Asserting or
negating the FPM bit selects full-port or reduced-port mode, respectively. When writing to the PCR, the
PCR LSB must be written to a logic zero. Setting the LSB of the PCR enables factory debug mode and
prevents the transmission of Nexus messages.
Table 30-13 describes the NDI configuration options.
Table 30-13. NDI Configuration Options
JCOMP Asserted
MCKO_EN bit of the
Port Configuration Register
FPM bit of the
Port Configuration Register
Configuration
No
X
Yes
0
Yes
1
Yes
1
X
Reset
X
Disabled
1
Full-port mode
0
Reduced-port mode
30.7.4 Programmable MCKO Frequency
MCKO is an output clock to the development tools used for the timing of MSEO and MDO pin functions.
MCKO is derived from the system clock, and its frequency is determined by the value of the MCKO_DIV
field in the port configuration register (PCR) located in the NPC. Possible operating frequencies include
one-quarter and one-eighth system clock speed.
Figure 30-14 shows the MCKO_DIV encodings. In this table, SYS_CLK represents the system clock
frequency. The default value selected if a reserved encoding is programmed is SYS_CLK2
NOTE
On PXD20, the pad type used for the Nexus3 signals will not support the
default SYSCLK2 and SYSCLKsetting, so the user must change the
MCKO frequency to be not faster than SYSCLK4.
Freescale Semiconductor
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
30-17