Users Manual

GSM/GPRS Module Series
M66 Hardware Design
M66_Hardware_Design Confidential / Released 40 / 82
Figure 16: Reference Design for UART Port with Hardware Flow Control
3.7.1.3. Firmware Upgrade
The TXD, RXD can be used to upgrade firmware. The PWRKEY pin must be pulled down before firmware
upgrade. The reference circuit is shown as below:
Figure 17: Reference Design for Firmware Upgrade
The firmware of module might need to be upgraded due to certain reasons. It is recommended to reserve
these pins in the host board for firmware upgrade.
3.7.2. Debug Port
 Two lines: DBG_TXD and DBG_RXD.
 It outputs log information automatically.
 Debug Port is only used for firmware debugging and its baud rate must be configured as 460800bps.
NOTE