UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 216

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

(1) Timer register 0 (TM0)
(2) Compare registers (CR00/CR01)
(3) Capture register (CR02)
(4) Edge detection circuit
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TM0 is a timer register that counts up using the count clock specified by the low-order 4 bits of prescaler mode register 0
(PRM0).
The count operation is stopped or enabled by means of timer control register 0 (TMC0).
TM0 can be read only with a 16-bit manipulation instruction. When RESET is input, TM0 is cleared to 0000H and the count
is stopped.
Caution Although the timer register can be read, if counting up the timer and reading the timer register conflict,
CR00 and CR01 are 16-bit registers that hold the values that determine the interval timer frequency.
If the CR00/CR01 contents match the contents of TM0, an interrupt request (INTC00/INTC01) and timer output control
signal are generated. Also, the count value can be cleared by a content match (CR01).
CR00 and CR01 can be read or written with a 16-bit manipulation instruction. The contents of these registers are undefined
after RESET input.
CR02 is a 16-bit register that captures the contents of TM0.
The capture operation is synchronized with the input of a valid edge (capture trigger) on the external interrupt request input
pin (INTP3). The contents of the CR02 are retained until the next capture trigger is generated.
CR02 can be read only with a 16-bit manipulation instruction. The contents of this register are undefined after RESET input.
The edge detection circuit detects an external input valid edge.
When the valid edge set by external interrupt mode register 1 (INTM1) is detected in the INTP3 pin input, the external
interrupt request (INTP3), a capture trigger, and a external event count clock are generated (see Figure 19-2 for details
of the INTM1).
the read value of the timer register may be illegal. Therefore, do not read the timer register if at all
possible.
If it is necessary to read the timer register, read it two or more times in a row in software, and assume
the value of the timer register is correct only when all the read values match.
CHAPTER 8 TIMER/COUNTER 0