Setting the Baud Rate

The upper limit of the baud rate depends on the communication specifications of the connected device, the quality of the cable used, the processing power (operation speed) of the PC used, and the load (Execute simultaneously with other programs, etc.).
Also, in the case of RS-422A/485 communication, the cable length can be extended up to 1200m, but if the communication distance is increased, the baud rate must be lowered.

Therefore, even if the baud rate is within the baud rate listed in the device specifications table, communication at a speed exceeding this upper limit will cause communication errors (overrun, parity, framing).
Confirm the baud rate that can be set by actually communicating with the diagnostic program.

The baud rate that can be set depends on the specifications of communication LSI installed on the device.
The overview is shown below, but for details of the baud rate that can be set, refer to the manual of each device.

The devices in the following table determine the baud rate that can be set.
Please note that baud rates not listed in the table cannot be set.

Target Device

Baud Rate
bps (bit/s)

COM-1(USB)H
COM-1P(USB)H
COM-1PD(USB)H

300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600, 115200, 230400, 460800, 921600

The devices in the following table can flexibly set the baud rate according to the reference clock for calculation.
Typical baud rate setting examples are shown in the table, but there are other baud rates that can be set.

Target Device	Baud Rate bps (b/s)			Reference clock for calculation
Target Device	Minimum Value	Maximum Value	Setting Example
COM-4CN-USB COM-4PDHN-USB	300	921600	300, 600, 1200, 2000, 2400, 4800, 9600, 19200, 38400, 76800 Setup error 0.1603% 115200, 153600, 230400, 460800, 921600	48,000,000
COM-1C-LPE COM-2C-LPE COM-2C-PE COM-4C-LPE COM-4C-PE COM-8C-LPE COM-8C-PE COM-2PC-PE COM-2PD-PE COM-4PC-PE COM-4PD-PE COM-1(LPCI)H COM-2(LPCI)H COM-2(PCI)H COM-4(LPCI)H COM-4(PCI)H (Board No.7190C or earlier)COM-8(PCI)H COM-8C-LPCI COM-1PD(LPCI)H COM-2PD(LPCI)H COM-2PD(PCI)H COM-4PD(PCI)H	15	921600	15, 50, 75, 150, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600, 14400, 19200, 28800, 38400, 57600, 76800, 115200, 153600, 230400, 460800, 921600	921,600
COM-1PDH-LPE COM-2PD-LPE COM-4(PCI)H (Board No.7190D or later)	30	921600	30, 50, 75, 150, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600, 14400, 19200, 28800, 38400, 57600, 76800, 115200, 153600, 230400, 460800, 921600	921,600
COM-2CL-PCI COM-2DL-PCI COM-4CL-PCI COM-4DL-PCI	15	230400	15, 50, 75, 150, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600, 14400, 19200, 28800, 38400, 57600, 76800, 115200, 153600, 230400	921,600
* Only supported when used in combination with CPS-BXC200 CPS-COM-1PC CPS-COM-1PD CPS-COM-2PC CPS-COM-2PD	15	921600	15, 50, 75, 150, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600, 14400, 19200, 28800, 38400, 57600, 76800, 115200, 153600, 230400, 460800, 921600	921,600
(BX-M210 GPIO modelEXT-A and EXT-B) COM-1C COM-1D	50	115200	50, 75, 150, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600, 14400, 19200, 28800, 38400, 57600, 115200	115,200

Division register value (Clock Divisor)

Set the division register of the LSI installed on the device with an integer value.

If the baud rate to be specified is not an integral multiple of the reference clock for calculation, the decimal point is rounded off and set to the LSI frequency division register (Clock Divisor).
Therefore, depending on the specified baud rate, a setup error may occur when setting the device baud rate.

In general, if the baud rate error is less than 1%, serial communication can be performed without error.
However, please make sure that the baud rate is configurable by actually communicating with the device.

Even if the calculation result of the setting value for the frequency division register is an integer, the maximum baud rate of the device used cannot be exceeded.

<Calculation formula for setting value to frequency division register>
Division register(Clock Divisor) = Reference clock for calculation / Specified baud rate

Example where setup error does not occur: (For COM-4CN-USB)

Reference clock for calculation = 48,000,000Hz(48MHz), Specified baud rate 9,600[bps]
Since the calculation result is 5,000, the setting to the division register is 5,000, and no setup error occurs.

(Details)
  Division register(Clock Divisor) = Reference clock for calculation / Specified baud rate
            = 48,000,000Hz / 9,600bps
            = 5,000

  Operation baud rate[bps] = Reference clock for calculation / Division registe value that you set
            = 48,000,000Hz / 5,000
            = 9,600bps

  Setup error[%] = ((Operation baud rate - Specified baud rate) / Specified baud rate) *100
            = ((9,600bps - 9,600bps) / 9,600bps) * 100
            = 0%

Example where setup error occurs: (For COM-4CN-USB)

Internal clock for calculation = 48,000,000Hz(48MHz), Specified baud rate 115,200[bps]
Since the calculation result is 416.66666, the setting to the division register is 416, a setup error of 0.1603% will occur.

(Details)

  Division register(Clock Divisor) = Reference clock for calculation / Specified baud rate
            = 48,000,000Hz / 115,200bps
            = 416.66666      * 416 is set to the division register

  Operation baud rate[bps] = Reference clock for calculation / Division registe value that you set
            = 48,000,000Hz / 416
            = 115,384.6153bps

  Setup error[%] = ((Operation baud rate - Specified baud rate) / Specified baud rate) * 100
            = ((115,384.6153bps - 115,200bps) / 115,200bps) * 100
            = 0.1603%