Dear TI Team,
We are using 2 - MAX3221 (Rev M) devices in our application that requires communication with an embedded module (RS-232 port) and also a PC (RS232). The baud rate is 115.2kbps. The system is powered with a 3.3V supply.
In our application, we use a microcontroller with a single H/W UART module to drive both these MAX3221 devices. In order to facilitate this, we intend to use the following configuration.
- Tie the FORCEON pin of both the MAX3221 devices to 3.3V
- We toggle the !EN and !FORCEOFF pins to be able to receive/transmit from PC or other embedded module. We have the following commonly used scenarios,
Case (A) - Receive from Embedded Module and Transmit to PC
Embedded Module side - MAX3221 configuration
- FORCEON = High
- !EN = Low
- !FORCEOFF = Low
PC side - MAX3221 configuration
- FORCEON = High
- !EN = High
- !FORCEOFF = High
Case (B) - Receive from PC and Transmit to Embedded Module
Embedded Module side - MAX3221 configuration
- FORCEON = High
- !EN = High
- !FORCEOFF = High
PC side - MAX3221 configuration
- FORCEON = High
- !EN = Low
- !FORCEOFF = Low
We will be switching b/w the configurations depending on when we receive the interrupt from either the embedded module or PC.
In context of the above, i had the following queries
1) The datasheet specification is 100us for driver enable to valid data at the output and 200ns for receiver enable to valid output. Assuming we follow these specifications, do you see any other limitations with our proposed use scenario?
2) The datasheet specs the typical values, is there data on the max value? We intend to assess the max value and design the system accordingly.
3) On a separate note, do you see any limitation in using MAX3221 to drive about 20ft of cable @ 115.2kbps (this is the max distance b/w the embedded system and our controller)
Best Regards,
Sridhar
