HD404369 Datasheet, PDF (68/117 Pages) Hitachi Semiconductor – 4-bit HMCS400-Series microcomputer

HD404369 Series
T × (N + 1)
TMC3 = 0
(free-running
timer)
TMC3 = 1
(reload timer)
T × 256
T
T × (256 – N)
Notes: T: Input clock period supplied to counter. (The clock source and system clock division ratio are
determined by timer mode register C.)
N: Value of timer write register C. (When N = 255 ($FF), PWM output is fixed low.)
Figure 49 PWM Output Waveform
Registers for Timer C Operation: By using the following registers, timer C operation modes are selected
and the timer C count is read and written.
 Timer mode register C (TMC: $00D)
 Port mode register A (PMRA: $004)
 Timer write register C (TWCL: $00E, TWCU: $00F)
 Timer read register C (TRCL: $00E, TRCU: $00F)
• Timer mode register C (TMC: $00D): Four-bit write-only register that selects the free-running/reload
timer function, input clock source, and the prescaler division ratio as shown in figure 50. It is reset to $0
by MCU reset.
Writing to this register is valid from the second instruction execution cycle after the execution of the
previous timer mode register C write instruction. Setting timer C’s initialization by writing to timer
write register C (TWCL: $00E, TWCU: $00F) must be done after a mode change becomes valid.
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