h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 310

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 10 14-Bit PWM D/A
10.2
10.2.1
DACNT is a 14-bit readable/writable up-counter that increments on an input clock pulse. The
input clock is selected by the clock select bit (CKS) in DACR. The CPU can read and write the
DACNT value, but since DACNT is a 16-bit register, data transfers between it and the CPU are
performed using a temporary register (TEMP). See section 10.3, Bus Master Interface, for details.
DACNT functions as the time base for both PWM D/A channels. When a channel operates with
14-bit precision, it uses all DACNT bits. When a channel operates with 12-bit precision, it uses the
lower 12 (counter) bits and ignores the upper two (counter) bits.
DACNT is initialized to H'0003 by a reset, in the standby modes, watch mode, subactive mode,
subsleep mode, and module stop mode, and by the PWME bit.
Bit 1 of DACNTL (CPU) is not used, and is always read as 1.
DACNTL Bit 0—Register Select (REGS): DADRA and DACR, and DADRB and DACNT, are
located at the same addresses. The REGS bit specifies which registers can be accessed. The REGS
bit can be accessed regardless of whether DADRB or DACNT is selected.
Bit 0
REGS
0
1
Rev. 4.00 Jun 06, 2006 page 256 of 1004
REJ09B0301-0400
Bit (CPU)
BIT (Counter)
Initial value
Read/Write
Register Descriptions
PWM D/A Counter (DACNT)
Description
DADRA and DADRB can be accessed
DACR and DACNT can be accessed
R/W
15
7
0
R/W
14
6
0
R/W
13
5
0
DACNTH
R/W
12
4
0
R/W
11
3
0
R/W
10
2
0
R/W
9
1
0
R/W
8
0
0
R/W
7
8
0
R/W
6
9
0
R/W
10
5
0
DACNTL
R/W
11
4
0
R/W
12
3
0
R/W
13
2
0
(Initial value)
—
—
—
1
1
REGS
R/W
—
0
1