455A Datasheet, PDF (31/148 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

455A Group
The 455A Group timer consists of the following circuits.
• Prescaler : 8-bit programmable timer
• Timer 1 : 8-bit programmable timer
• Timer 2 : 8-bit programmable timer
• Timer 3 : 16-bit fixed frequency timer
• Timer LC : 4-bit programmable timer
• Watchdog timer: 16-bit fixed frequency timer
(Timers 1, 2 and 3 have the interrupt function, respectively)
Prescaler, timer 1, timer 2, timer 3 and timer LC can be
controlled with the timer control registers PA and W1 to W5. The
watchdog timer is a free counter which is not controlled with the
control register.
Each function is described below.
Table 16 Function related timers
Circuit
Structure
Prescaler 8-bit programmable
binary down counter
Count source
• Instruction clock (INSTCK)
Timer 1
Timer 2
Timer 3
8-bit programmable
binary down counter
(link to INT input)
(carrier wave output auto-
control function)
8-bit programmable
binary down counter
(with carrier wave
generation function)
16-bit fixed dividing
frequency
• PWM signal (PWMOUT)
• Prescaler output (ORCLK)
• Timer 3 underflow (T3UDF)
• CNTR input
• XIN input
• Prescaler output divided by 2
(ORCLK/2)
• XCIN input
• Prescaler output (ORCLK)
• High-speed on-chip oscillator
(f(HSOCO))
• Low-speed on-chip oscillator
(f(LSOCO))
Timer LC 4-bit programmable binary
down counter
Watchdog 16-bit fixed dividing
timer
frequency
• Bit 4 of timer 3 (T34)
• System clock (STCK)
• Instruction clock (INSTCK)
Frequency
dividing ratio
Use of output signal
1 to 256
• Timer 1 count source
• Timer 2 count source
• Timer 3 count source
1 to 256 • CNTR output control
• Timer 1 interrupt
Control
register
PA
W1
W4
1 to 256 • Timer 1 count source
W2
• CNTR output
W4
• Timer 2 interrupt
512
• Timer 1 count source
W3
1024 • Timer LC count source
W5
2048 • Timer 3 interrupt
4096
8192
16384
32768
65536
1 to 16 • LCD clock
W4
65536 • System reset (counting twice)
-
• Decision of flag WDF1
Rev.1.01 Feb 15, 2008 Page 31 of 146
REJ03B0224-0101