PSD4235G2V_09 Datasheet, PDF (96/124 Pages) STMicroelectronics – Flash in-system programmable (ISP) peripherals for 16-bit MCUs (3.3 V supply)

Programming in-circuit using the JTAG serial interface
PSD4235G2V
22 Programming in-circuit using the JTAG serial
interface
Note:
The JTAG Serial Interface on the PSD can be enabled on Port E (see Table 51). All memory
blocks (primary Flash memory and secondary Flash memory), PLD logic, and PSD
Configuration bits may be programmed through the JTAG-ISC Serial Interface. A blank
device can be mounted on a printed circuit board and programmed using JTAG In-System
Programming (ISP).
The standard JTAG signals (IEEE 1149.1) are TMS, TCK, TDI, and TDO. Two additional
signals, TSTAT and TERR, are optional JTAG extensions used to speed up Program and
Erase cycles.
By default, on a blank PSD (as shipped from the factory, or after erasure), four pins on Port
E are enabled for the basic JTAG signals TMS, TCK, TDI, and TDO.
See Application Note AN1153 for more details on JTAG In-System Programming (ISP).
22.1
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 device, 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 is 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 Express_enabled +
/* An NVM configuration bit inside the PSD is set by the designer
in the PSDsoft Express 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 20 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 tie
logically the node JTAGSEL to the JEN\ signal on the Flashlink cable
when multiplexing JTAG signals. See Application Note 1153 for
details. */
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