Ring Oscillator Control Registers; Ringosc Control Register (Mrctl) - NEC V850ES/DJ2 User Manual

5.2 Ring Oscillator Control Registers

5.2.1 RingOSC Control Register (MRCTL)

The MRCTL register is an 8-bit register that controls the RingOSC operation.
This register can be read or written in 8-bit units. However, bits 1 (MRCALSF) and 0 (MRCALERR) are
read-only.
Cautions: 1. After system reset has been released, the MRCALEN bit can be written only one
time.
2. When the MRON bit = 0, the MRCLKSEL bit can't be written.
Figure 5-1: RingOSC Control Register (MRCTL) Format (1/2)
7
MRCTL MRON MRCLKSEL
After Reset 0
R/W R/W R/W
MRON
0 Ring Oscillator stopped
1 Ring Oscillator enabled
This bit will be set when MRCLKSEL = 1 and a rising edge at MTCSP pin occurs.
Cautions: 1. After MTRESET and MTCS = "1" the MRON bit is changed from "0" to "1" by hard-
ware.
2. To save power consumption the Ring Oscillator can be stopped by clearing the
MRON bit to "0". After that, the MTRC has to be woken up via the PCM0/CS signal.
The MRCAL register has to be updated, too.
MRCLKSEL
0 CLK as input for clock supply by FG2
1 internal Ring Oscillator as clock source
Caution: If MRON bit = "0" (Ring Oscillator stopped for power saving) no MTRC register
access is possible. Therefor the MRON bit can't be set to "1" (Ring Oscillator as
clock source)
Chapter 5 Clock Generator
6 5 4
0 MRCALEN
1 0 1
R R/W
Operation / Stop of RingOSC and MRNGCTL operation control
System clock selection for meter
Preliminary User's Manual U17763EE1V1UD00
3 2 1
0 0 MRCALSF MRCALERR
0 0 0
R R R
0 Address Initial value
0x2E 0x50
0
R
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