ZTE Corporation ZTEMC2261 Manuale Utente
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18
MC2261
Hardware Development Guide of Module Product
Figure 3–2 USB Typical Circuit
3.4. UART
Pins of MSM_CTS, MSM_RTS, MSM_RXD and MSM_TXD are 1.8V level respectively for the external interface, when connecting
with level circuit which is not 1.8V will need the level switch connection. Pins of MO_RI, DCD, DTR and DSR are the level of 2.85V
respectively for the external interface, when connecting with level circuit which is not 2.85V will need the level switch connection.
Otherwise, UART will be unstable or module will be damaged because of the unmatched level. Figure 3-3, 3-4 and 3-5 are the
references:
NOTES:
1
）UART must be led out[only requires the connection with RXD or TXD] for upgrading when use the module to do whole device design, USB for
software upgrading is the first choice.
2
）IO level is 1.8V or 2.85V. Level switch connection must be needed when 1.8V level is connected with the logic circuit which is not 1.8V[such as
MCU, RS232 or driver IC MAX3238], or when 2.85V level is connected with the logic circuit which is not 2.85V[for example, RS232 or driver IC
MAX3238]. Otherwise, level will be unstable or module will be damaged because of the unmatched level
3
）Only RXD and TXD are needed to be connected under the condition of no flow control. RXD, TXD, /CTS and /RTS are needed to be used when
selecting hardware flow control to connect other processors. All IO signal should be connected when the module is used as Modem to connect
with PC.
4
）Module won’t be hibernated if RxD is high level.
Figure 3–3 Wire serial level conversion circuit
Figure 3–4 wire serial level conversion circuit