Oki MSM66591, User Manual

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11-16
MSM66591/ML66592 User's Manual
Chapter 11 Flexible Timer (FTM)
If TM1 is selected as the timer for connecting to type A1 register module, 4 bits of TM0L
are latched to TMRnL at the time TM1 is latched to TMRn.
Type A1 register modules have no "function to check a cycle of the timer counter
between capture events," which is used for the capture function of type D and E register
modules.
11.3.3 Capture Pin Dividing Circuit
The MSM66591/ML66592 type A1 timer register modules have a capture pin dividing
circuit that can perform division from 1/1 to 1/64.
[1] Configuration of Dividing Circuit
The dividing circuit consists of the following:
• counter to divide valid pulses input to capture pin (EVDVn) (n = 0–3)
• register to set dividing ratio (EVNTCONL, EVNTCONH)
• comparison circuit to compare counter value and register value
• register to hold dividing counter value when an event is generated (EVDVnBF) (n =
0–3)
[2] Operation of Dividing Circuit
If valid edges (pulses) are input to a capture pin, EVDVn counts their number. If the
counter value and the dividing value specified by EVNTCONL or EVNTCONH match, a
capture event is generated.
If a capture event is generated, a capture interrupt request is generated, the counter
value is loaded to the timer register, the EVDVn value is loaded to EVDVnBF, and
EVDVn is cleared to "0". (n = 0–3)
[3] Operation to Switch Dividing Ratio
Since the dividing ratio is programmable, the dividing operation may differ, depending
on the timing that changes the dividing ratio. In this case, the MSM66591/ML66592
operate as follows:
1) When the dividing ratio is changed from 1/N to 1/M (N > M), if a valid edge is input
to a capture pin when:
• counter value C in the dividing circuit is C
≥
M – 1 (except when M = 1)
or
• M = 1
a capture event is generated.
If a valid edge is input to a capture pin when:
• counter value C in the dividing circuit is C < M – 1 (except when M = 1)
a capture event is not generated, and the counter value in the dividing circuit is
incremented.
2) When the dividing ratio is changed from 1/N to 1/M (N < M), the dividing operation
continues until the counter value becomes M, and a capture event is generated
when the counter value becomes M.