SH7708 Datasheet, PDF (311/625 Pages) Renesas Technology Corp – SuperH™ RISC engine

Section 11 Timer (TMU)
11.1 Overview
The SH7708 Series uses a three-channel 32-bit timer unit (TMU).
11.1.1 Features
The TMU has the following features:
• Each channel is provided with an auto-reload 32-bit down counter
• Channel 2 is provided with an input capture function
• All channels are provided with 32-bit constant registers and 32-bit down counters that can be
read or written to at any time
• All channels generate interrupt requests when the 32-bit down counter underflows (H'00000000
→ H'FFFFFFFF)
• Allows selection between 6 counter input clocks: External clock (TCLK), on-chip RTC output
clock (16 kHz), Pφ/4, Pφ/16, Pφ/64, Pφ/256. (Pφ is the internal clock for peripheral modules
and can be selected as 1/4, 1/2, or the same frequency as that of the CPU operating clock φ.)
See section 9, On-Chip Oscillation Circuits, for more information on the clock pulse
generator.
• All channels can operate when the SH7708 Series is in standby mode: When the RTC output
clock is being used as the counter input clock, the SH7708 Series is still able to count in
standby mode.
• Synchronized read: TCNT is a sequentially changing 32-bit register. Since the peripheral
module used has an internal bus width of 16 bits, a time lag can occur between the time when
the upper 16 bits and lower 16 bits are read. To correct the discrepancy in the counter read value
caused by this time lag, a synchronization circuit is built into the TCNT so that the entire 32-
bit data in the TCNT can be read at once.
• The maximum operating frequency of the 32-bit counter is 2 MHz on all channels: Operate the
SH7708 Series so that the clock input to the timer counters of each channel (obtained by
dividing the external clock and internal clock with the prescaler) does not exceed the maximum
operating frequency.
1 1 . 1 . 2 Block Diagram
Figure 11.1 shows a block diagram of the TMU.
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