h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 312

• 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
Bits 15 to 3—PWM D/A Data 13 to 0 (DA13 to DA0): The digital value to be converted to an
analog value is set in the upper 14 bits of the PWM D/A data register.
In each base cycle, the DACNT value is continually compared with these upper 14 bits to
determine the duty cycle of the output waveform, and to decide whether to output a fine-
adjustment pulse equal in width to the resolution. To enable this operation, the data register must
be set within a range that depends on the carrier frequency select bit (CFS). If the DADR value is
outside this range, the PWM output is held constant.
A channel can be operated with 12-bit precision by keeping the two lowest data bits (DA0 and
DA1) cleared to 0 and writing the data to be converted in the upper 12 bits. The two lowest data
bits correspond to the two highest counter (DACNT) bits.
Bit 1—Carrier Frequency Select (CFS)
Bit 1
CFS
0
1
DADRA Bit 0—Reserved: This bit cannot be modified and is always read as 1.
DADRB 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 258 of 1004
REJ09B0301-0400
Description
Base cycle = resolution (T)
DADR range = H'0401 to H'FFFD
Base cycle = resolution (T)
DADR range = H'0103 to H'FFFF
Description
DADRA and DADRB can be accessed
DACR and DACNT can be accessed
64
256
(Initial value)
(Initial value)