Moxa DA-682A-C7-W7E [12/42] Non standard baudrates

DA-682A Series Hardware Introduction

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Non-standard Baudrates

Moxa’s UART ASIC, which is used for both the DA-SP08-I-DB and DA-SP08-I-TB serial expansion modules,

supports most non-standard baudrates in the range 50 bps to 921.6 Kbps. In fact, supported baudrates are

much denser towards the lower values. For example, no baudrates are supported between the integers 5320

and 5323, but 49 baudrates are supported between the integers 387 and 388. Of course this is the way it

should be, since serial devices that require using non-standard baudrates generally use slower baudrates.

Before using a serial device that requires using a non-standard baudrate, you must first check that the

DA-682A supports a baudrate within the tolerance specified by the serial device manufacturer.

Use the following formula to calculate which baudrates are supported by the DA-283:

(A) Baudrate = 921600/(N+M/8) bps, for N = 1, 2, …, 18431, M = 0, 1, 2, …, 7

(B) Baudrate = 8 x 921600/K bps, for K = 8, 9, …, 147456

If you are a programmer and you need to write a driver for your serial device, then you may need to use

formula A. If you have a serial device that requires using a non-standard baudrate, then you can use formula

B to determine if the DA-682A supports a baudrate within the tolerance specified by the serial device

manufacturer.

Example: Your serial device requires using a baudrate of 5340 bps and has a tolerance of 2 bps. Can the

DA-682A be used with this device?

Solution: Set formula B to the desired baudrate and then solve for K.

8 x 912600/K = 5338 ==> K = 1367.703259…

This shows that the supported baudrate closest to 5340 comes from setting K=1367 or K=1368.

K=1368 ==> Baudrate1 = 5336.842105...

K=1367 ==> Baudrate2 = 5340.746159…

Since 5338 – Baudrate1 < 2, we can see that the DA-682A supports the serial device.

Note that we can use formula A to generate the so-called “standard” baudrates, which come from setting M=0,

and setting N equal to certain integers.

Standard Baudrates

Baudrate N M Baudrate N M

921600 1 0 4800 192 0

460800

2400

384

230400 4 0 1800 512 0

115200 8 0 1200 768 0

57600 16 0 600 1536 0

38400 24 0 300 3072 0

19200 48 0 150 6144 0

9600 96 0 75 12288 0

7200 128 0 50 18432 0

WARNING

ommunication between a serial device and a Moxa UART port may not work correctly if the serial device use

a baudrate that

it not within the correct tolerance of a baudrate calculated from either formula A or formula B