UPD784938 Datasheet, PDF (375/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 12 TIMER 3
(1) Timer counter 3 (TM3/TM3W)
TM3/TM3W is a timer counter 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 (TM3)
or 16-bit mode (TM3W) 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.
(2) Compare register (CR30/CR30W)
CR30/CR30W is an 8/16-bit register 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 is 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.
CR30 can be read or written to with an 8/16-bit manipulation instruction. The contents of CR30 are undefined after
RESET input.
(3) Prescaler
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 TM3/TN3W to perform count operations.
(4) Selector
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 TM3/TM3W.
Preliminary User’s Manual U13987EJ1V0UM00
375