Baud Rate Setting

The upper limit of the baud rate is determined by the communication specifications of the connected device, the quality of the cable used, the processing capacity (operating speed) and the load (simultaneous execution with other programs, etc.) of the PC being used.
Additionally, 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 specification table, communicating at a speed exceeding this upper limit may cause communication errors (overrun, parity, framing).
Please actually perform communication using the Diagnosis Program, etc., and check the configurable baud rate.

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

The devices in the table below have fixed baud rate that can be set.
Please note that baud rate not listed in the table cannot be set.

Target device

Configurable baud rate
bps (bit per second)

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

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

The devices in the table below 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 rate that can be set.

Target device	Baud rate bps (bit per second)			Reference clock for calculation
Target device	Minimum value	Maximum value	Setting example
COM-4CN-USB COM-4PDHN-USB	300	921600	300, 600, 1200, 2400, 4800, 9600, 19200 Setting error 0.1603% 　115200, 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 number 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	50	921600	50, 75, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600	921,600
COM-1PDH-LPE COM-2PD-LPE COM-4(PCI)H ※Board number No.7190D or later	50	921600	50, 75, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600	921,600
COM-2CL-PCI COM-2DL-PCI COM-4CL-PCI COM-4DL-PCI	50	230400	50, 75, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400	921,600
※Compatible only when used with CPS-BXC200 CPS-COM-1PC CPS-COM-1PD CPS-COM-2PC CPS-COM-2PD	50	921600	50, 75, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600	921,600
(EXT-A, EXT-B on BX-M210 GPIO model） COM-1C COM-1D	50	115200	50, 75, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200	115,200

Value of frequency division register (Clock Divisor)

The frequency division register of the LSI installed in the device is set with an integer value.

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

Generally, if the baud rate error is less than 1%, serial communication is possible without any errors.
However, please confirm that the baud rate is configurable by actually communicating with the device.

In addition, even if the calculation result of the setting value to the frequency division register is an integer, it cannot be set to a value exceeding the maximum baud rate of the device being used.

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

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

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

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

Operating baud rate [bps] ＝ Reference clock for calculation ÷ Set value of frequency division register
　　　　　　　　　　　　　　＝ 48,000,000Hz ÷ 5,000
　　　　　　　　　　　　　　＝ 9,600bps

Setting error [%] ＝ ((Operating baud rate － Specified baud rate) ÷ Specified baud rate) ｘ 100
　　　　　　　　　　＝ ((9,600bps － 9,600bps) ÷ 9,600bps) ｘ 100
　　　　　　　　　　＝ 0%

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

Reference clock for calculation＝48,000,000Hz(48MHz), Specified baud rate 115,200[bps]
The calculation result is 416.66666, so the setting value to the frequency division register is 416, which causes a setting error of 0.1603%.

(Details)

Frequency division register (Clock Divisor) ＝ Reference clock for calculation ÷ Specified baud rate
　　　　　　　　　　　　　　＝ 48,000,000Hz ÷ 115,200bps
　　　　　　　　　　　　　　＝ 416.66666　　　※416 is set to the frequency division register

Operating baud rate [bps] ＝ Reference clock for calculation ÷ Set value of frequency division register
　　　　　　　　　　　　　　＝ 48,000,000Hz ÷ 416
　　　　　　　　　　　　　　＝ 115,384.6153bps

Setting error [%] ＝ ((Operating baud rate － Specified baud rate) ÷ Specified baud rate) ｘ 100
　　　　　　　　　　＝ ((115,384.6153bps － 115,200bps) ÷ 115,200bps) ｘ 100
　　　　　　　　　　＝ 0.1603%