R01UH0823EJ0100 Rev.1.00 Page 217 of 1823
Jul 31, 2019
RX23W Group 10. Clock Frequency Accuracy Measurement Circuit (CAC)
10.2.6 CAC Upper-Limit Value Setting Register (CAULVR)
CAULVR is a 16-bit readable/writable register that specifies the upper-limit value of the counter used for measuring the
frequency. When the frequency rises above the value specified in this register, a frequency error is detected.
Write to this register when the CACR0.CFME bit is 0.
The counter value held in CACNTBR can vary with the difference between the phases of the digital filter and edge-
detection circuit on the one hand and the signal on the CACREF pin on the other, so ensure that this setting allows an
adequate margin.
10.2.7 CAC Lower-Limit Value Setting Register (CALLVR)
CALLVR is a 16-bit readable/writable register that specifies the lower-limit value of the counter used for measuring the
frequency. When the frequency falls below the value specified in this register, a frequency error is detected.
Write to this register when the CACR0.CFME bit is 0.
The counter value held in CACNTBR can vary with the difference between the phases of the digital filter and edge-
detection circuit on the one hand and the signal on the CACREF pin on the other, so ensure that this setting allows an
adequate margin.
10.2.8 CAC Counter Buffer Register (CACNTBR)
CACNTBR is a 16-bit read-only register that retains the counter value at the time a valid reference signal edge is input.
Address(es): 0008 B006h
b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
Value after reset:
0000000000000000
Address(es): 0008 B008h
b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
Value after reset:
0000000000000000
Address(es): 0008 B00Ah
b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
Value after reset:
0000000000000000
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