What are the minimum connections required for programming modules?

1) Connect power and ground on pins 24 (VDD), 25 (GND) & 26 (VSSA).

2) Ensure that pins 9 (SSZ) and 13 (SSM) are tied together. This allows the SPI Select signal from the JN5121 device to communicate with the FLASH.

3) Disable the write protect on the FLASH by tying pin 14 (SWP) HIGH.

4) To ensure correct power up, the reset circuit shown below must be applied to pin 29 (RESETN). If required a switch can be applied between RESETN and GROUND.

5) At power up or reset the Boot Loader first looks at pin 7 (MISO) to determine whether to go into programming mode. To enter programming mode, pin 7 (MISO) must be held LOW at power up or reset and then released.

6) Serial communications are made on pins 18 & 19 (TXD, RXD). These signal levels must be level shifted to 3.3V.

If you are using the Jennic serial dongle to level shift then a signal (PGM) is available to put the device into programming mode. This signal should be connected to the module as shown below.

Note:
Some terminal programs i.e. Hyperterminal pull the serial PGM/RTS line down by default, thus, setting the device into programming mode at power on/reset. After programming, when powering on the module, ensure you have quit or disconnected hyperterminal or disconnect the serial lead.

References: 'Module Development' Reference Manual