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RL78/F13, F14 CHAPTER 9 REAL-TIME CLOCK

R01UH0368EJ0210 Rev.2.10 674

Dec 10, 2015

9.3.16 16-bit watch error correction register (SUBCUDW)

This register is used to correct the watch with high accuracy when it is slow or fast by changing the value that overflows

from the internal counter (16 bits) to the second count register (SEC) (reference value: 7FFFH).

Set the SUBCUDW register by a 16-bit memory manipulation instruction.

Reset signal generation clears this register to 0000H.

Figure 9-17. Format of 16-Bit Watch Error Correction Register (SUBCUDW)

Address: FFF54H After reset: 0000H R/W

Symbol 15 14 13 12 11 10 9 8

SUBCUDW DEV - - F12 F11 F10 F9 F8

7 6 5 4 3 2 1 0

F7 F6 F5 F4 F3 F2 F1 F0

DEV Setting of watch error correction timing

0 Corrects watch error when the second digits are at 00, 20, or 40 (every 20 seconds).

1 Corrects watch error only when the second digits are at 00 (every 60 seconds).

Writing to the SUBCUDW register at the following timing is prohibited.

 When DEV = 0 is set: For a period of SEC = 00H, 20H, 40H

 When DEV = 1 is set: For a period of SEC = 00H

F12 Setting of watch error correction value

0 Increases by {(F11, F10, F9, F8, F7, F6, F5, F4, F3, F2, F1, F0) – 1}  2.

1 Decreases by {(/F11, /F10, /F9, /F8, /F7, /F6, /F5, /F4, /F3, /F2, /F1, /F0) + 1}  2.

When (F12, F11, F10, F9, F8, F7, F6, F5, F4, F3, F2, F1, F0) = (*, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, *), the watch error is

not corrected.

Range of correction value: (when F12 = 0) 2, 4, 6, 8, … , 8184, 8186, 8188

(when F12 = 1) –2, –4, –6, –8, … , –8184, –8186, –8188

Cautions 1. / of /Fn (n = 0 to 11) means invert.

2. * means 0 or 1.

The range of value that can be corrected by using the 16-bit watch error correction register (SUBCUDW) is shown

below.

DEV = 0 (correction every 20 seconds) DEV = 1 (correction every 60 seconds)

Correctable range –12496.9 ppm to 12496.9 ppm –4165.6 ppm to 4165.6 ppm

Maximum excludes

quantization error

1.53 ppm0.51 ppm

Minimum resolution 3.05 ppm 1.02 ppm

Remark If a correctable range is −4165.6 ppm or lower and 4165.6 ppm or higher, set DEV to 0.

Renesas RL78/D1A User Manual

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