UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 385

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

(1) Timer register 3 (TM3/TM3W)
(2) Compare register (CR30/CR30W)
(3) Prescaler
(4) Selector
TM3/TM3W are timer registers that count up using the count clock specified by the high-order 4 bits of prescaler mode
register 0 (PRM0).
The count operation is stopped or enabled by the timer control register 0 (TMC0). In addition, an 8-bit mode (TM1)
or 16-bit mode (TM1W) can be selected.
TM3 can be read only with an 8/16-bit manipulation instruction.
When RESET is input, TM3 is cleared to 00H and the count is stopped.
CR30/CR30W are 8/16-bit registers that hold the value that determines the interval timer frequency.
If the CR30/CR30W contents match the contents of TM3/TM3W, the contents of TM3/TM3W are cleared automatically
and an interrupt request (INTC30) is generated.
This compare register operates as CR30 in the 8-bit mode and CR30W in the 16-bit mode.
The CR30 register can be read or written to with an 8/16-bit manipulation instruction. The contents of CR30 are
undefined after RESET input.
The prescaler generates the count clock from the internal system clock. The clock generated by the prescaler is selected
by the selector, and is used as the count clock by the timer to perform count operations.
The selector selects a signal resulting from dividing the internal clock or the edge detected by the edge detection circuit
as the count clock of timer register 3 (TM3/TM3W).
Caution Although the timer register can be read, if counting up the timer and reading the timer register conflict,
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 coincide.
CHAPTER 11 TIMER 3
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