Bit Rate Measurement - Renesas RX100 Series User Manual

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Bit Rate Measurement

The bit rate measurement function measures the intervals between rising and falling edges and between falling and rising

edges of the signal input from the RXDX12 pin. Figure 23.70 shows an example of operations for bit rate measurement.

(1) Writing 1 to the CR0.BRME bit enables bit rate measurement. Only set the BRME bit to 1 when you wish to

proceed with bit rate measurement. Furthermore, bit rate measurement will not proceed during a Break Field, even

if the BRME bit is set to 1.

(2) After detection of the Break Field low width, bit rate measurement starts when the level input on the RXDX12 pin

becomes high.

(3) Once bit rate measurement has started, counter values from the timer are retained in the read buffers on the input of

valid edges from the RXDX12 pin (rising and falling edges) and the counter is reloaded. An SCIX3 interrupt is also

generated if the value of the ICR.AEDIE bit is 1. Retention by registers TCNT and TPRE is released by reading

these registers.

(4) The bit rate as calculated from the values counted during intervals between valid edges can be used for adjusting the

rate by changing the settings of the BRR register. To disable the bit rate measurement after a match with Control

Field 1, write 0 to the CR0.BRME bit.

Counter value

Read buffer*

Note 1. The TCNT or TPRE register indicates the contents of the read buffers.

Note 2. The STR.AEDF flag becomes 1 on detection of a valid edge.

Note 3. When an effective edge is detected, the current value of the counter is stored in the read buffer.

Note 4. The value retained in the read buffers due to one valid edge is not updated to the new value even if a further valid edge is detected.

Note 5. Retention of a value in a read buffer due to a valid edge is released by reading the TCNT or TPRE register.

Figure 23.70

Example of Operations for Bit Rate Measurement

R01UH0822EJ0100 Rev.1.00

Jul 31, 2019

23. Serial Communications Interface (SCIg, SCIh)

Retention released

Read the counter value*

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