7220 Datasheet, PDF (93/303 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

FUNCTIONAL DESCRIPTION
2.10 PWM
Set “2C16” to DA-H register.
Set “2816” to DA-L register.
b7 b6 b5 b4 b3 b2 b1 b0
[DA-H 0 _{0 1 0 1 1 0 0} DH
register]
At writing of DA-L
b7 b6 b5 b4 b3 b2 b1 b0
[DA-L register]
1 0 1 0 0 0 DL
Undefined
At writing of DA-L
b13
b6 b5
b0
[DA latch] 0 0 1 0 1 1 0 0 1 0 1 0 0 0
HIGH level area of
fundamental waveform
These bits decide HIGH level area
of fundamental waveform.
=
Minimum
resolution bit
width 0.25 µs
!
High-order 8-bit
value of DA latch
These bits decide smaller interval “tm” in which HIGH level
area is [HIGH level area of fundamental waveform + τ ].
Fundamental
waveform
0.25 µs ! 44
14-bit
PWM output ^{2C 2B 2A … 03 02 01 00}
8-bit
counter
FF FE FD ^… D6 D5 D4 D3 ^… 02 01 00
Fundamental waveform of smaller interval
“tm” which is not specified by low-order 6
bits is not changed.
0.25 µs ! 44
Waveform of smaller interval “tm” specified by low-order 6 bits
0.25 µs ! 45
14-bit
PWM output
2C
2B
2A
…
03
02 01
00
0.25 µs
8-bit
counter
FF FE FD ^… D6 D5 D4 D3 ^… 02 01 00
τ = 0.25 µs
14-bit PWM output
Low-order 6-bit output
of DA latch
t0
t1
t2
t3
t4
t5
t59 t60 t61 t62 t63
Repeat period
T = 4096 µs
Fig. 2.10.3 14-bit PWM output example (f(XIN) = 8 MHz)
2-66
7220 Group User’s Manual