p2125vps20 Renesas Electronics Corporation., p2125vps20 Datasheet - Page 278

• Manufacturer Part Number: p2125vps20
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 11 16-Bit Free-Running Timer (FRT)
11.7.4
When the internal clock is changed, the changeover may source FRC to increment. This depends
on the time at which the clock is switched (bits CKS1 and CKS0 are rewritten), as shown in table
11.3.
When an internal clock is used, the FRC clock is generated on detection of the falling edge of the
internal clock scaled from the system clock (φ). If the clock is changed when the old source is high
and the new source is low, as in case no. 3 in table 11.3, the changeover is regarded as a falling
edge that triggers the FRC clock, and FRC is incremented. Switching between an internal clock
and external clock can also source FRC to increment.
Rev. 1.00 Sep. 21, 2006 Page 240 of 658
REJ09B0310-0100
Switching of Internal Clock and FRC Operation
Figure 11.20 Conflict between OCR Write and Compare-Match
Compare-match signal
Internal write signal
OCRAR (OCRAF)
(When Automatic Addition Function is Used)
Address
OCR
FRC
φ
Automatic addition is not performed
because compare-match signals are disabled.
OCRAR (OCRAF)
address
Disabled
Old data
N
N
New data
N+1