
PSD835G2  
PSD8XX Family
71
9.6.1   Standard JTAG Signals
The standard JTAG signals (TMS, TCK, TDI, and TDO) can be enabled by any of three 
different conditions that are logically ORed. When enabled, TDI, TDO, TCK, and TMS are
inputs, waiting for a serial command from an external JTAG controller device (such as
FlashLink or Automated Test Equipment). When the enabling command is received from
the external JTAG controller, TDO becomes an output and the JTAG channel is fully 
functional inside the PSD. The same command that enables the JTAG channel may
optionally enable the two additional JTAG pins, TSTAT and TERR. 
The following symbolic logic equation specifies the conditions enabling the four basic 
JTAG pins (TMS, TCK, TDI, and TDO) on their respective Port E pins. For purposes of 
discussion, the logic label JTAG_ON will be used. When JTAG_ON is true, the four pins
are enabled for JTAG. When JTAG_ON is false, the four pins can be used for general PSD
I/O.
JTAG_ON = PSDsoft_enabled  +  
/* An NVM configuration bit inside the PSD is set by the designer 
in the PSDsoft Configuration utility.  This dedicates the pins for 
JTAG at all times (compliant with IEEE 1149.1) */
Microcontroller_enabled  + 
/* The microcontroller can set a bit at run-time by writing to the 
PSD register, JTAG Enable. This register is located at address 
CSIOP + offset C7h. Setting the JTAG_ENABLE bit in this 
register will enable the pins for JTAG use. This bit is cleared 
by a PSD reset or the microcontroller. See Table 31 for bit 
definition. */
PSD_product_term_enabled;
/* A dedicated product term (PT) inside the PSD can be used to 
enable the JTAG pins. This PT has the reserved name 
JTAGSEL. Once defined as a node in PSDabel, the designer 
can write an equation for JTAGSEL. This method is used when 
the Port E JTAG pins are multiplexed with other I/O signals. 
It is recommended to logically tie the node JTAGSEL to the 
JEN\ signal on the Flashlink cable when multiplexing JTAG 
signals. See Application Note 54 for details.
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
*
*
*
*
*
*
*
JTAG_ENABLE
Table 31.  JTAG Enable Register
JTAG Enable
*
Bits 1-7 are not used and should set to 0.
Bit definitions:
JTAG_ENABLE 1 = JTAG Port is Enabled.
0 = JTAG Port is Disabled.
NOTE:
The state of the PSD reset input signal will not interrupt (or prevent) JTAG operations if
the JTAG pins are dedicated by an NVM configuration bit (via PSDsoft). However, the
PSD reset input will prevent or interrupt JTAG operations if the JTAG enable register is
used to enable the JTAG pins.
The 
PSD835G2
Functional
Blocks
(cont.)