HD404054 Datasheet, PDF (45/101 Pages) Hitachi Semiconductor – HMCS400-series microcomputers designed to increase program productivity with large-capacity memory

HD404054 Series/HD404094 Series
Timers
The MCU has three timer/counters (A, C, and D).
• Timer A: Free-running timer
• Timer C: Multifunction timer
• Timer D: Multifunction timer
Timer A is an 8-bit free-running timer. Timers C and D are 8-bit multifunction timers, whose functions are
listed in table 23. The operating modes are selected by software.
Timer A
Timer A Functions: Timer A has the following functions.
• Free-running timer
The block diagram of timer A is shown in figure 30.
Timer A Operations:
• Free-running timer operation: The input clock for timer A is selected by timer mode register A (TMA:
$008).
Timer A is reset to $00 by MCU reset and incremented at each input clock. If an input clock is applied
to timer A after it has reached $FF, an overflow is generated, and timer A is reset to $00. The overflow
sets the timer A interrupt request flag (IFTA: $001, bit 2). Timer A continues to be incremented after
reset to $00, and therefore it generates regular interrupts every 256 clocks.
Registers for Timer A Operation: Timer A operating modes are set by the following registers.
• Timer mode register A (TMA: $008): Four-bit write-only register that selects timer A’s operating mode
and input clock source as shown in figure 31.
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