32176 Datasheet, PDF (623/742 Pages) Renesas Technology Corp – 32-BIT RISC SINGLE-CHIP MICROCOMPUTER

18
OSCILLATOR CIRCUIT
18.1 Oscillator Circuit
18.1.3 Oscillation Drive Capability Select Function
The microcomputer incorporates a four-stage oscillation drive capability select function.
Once the oscillation of the oscillator circuit has stabilized, the XIN-XOUT drive capability can be lowered. The
lower the drive capability, the smaller the amount of power consumption.
Clock Control Register (CLKCR)
b0
1
2
3
4
5
XDRVP
0
0
0
0
0
0
6
b7
XDRV
1
1
b
Bit Name
0–4
No function assigned. Fix to "0".
5
XDRVP
XDRV write control bit
6–7
XDRV
XIN-XOUT drive capability select bit
<Address: H’0080 0786>
Function
<Upon exiting reset: H’03>
RW
00
0W
XIN-XOUT drive capability (performance ratio)
00: Low
0.25
01:
0.50
10:
0.75
11: High
1.00
RW
(1) XDRV write control bit (XDRVP) (Bit 5)
This bit controls writing to the XIN-XOUT drive capability select bits.
(2) XIN-XOUT drive capability select bits (Bits 6, 7)
The following shows the procedure for writing to these bits.
1. Set the write control bit (XDRVP) to "1".
2. Immediately following the above, reset the write control bit (XDRVP) to "0" and write the appropriate value
to the XIN-XOUT drive capability select bits.
Note: • If a write cycle to any other area occurs between 1 and 2, write to XDRV has no effect and the
written value is not reflected. Therefore, disable interrupts and DMA transfers before setting
the drive capability control bits. Note that a pair of two consecutive writes comprise a write
operation.
32176 Group Hardware Manual
Rev.1.10 REJ09B0067-0110 Jun 20.06
18-5