CHAPTER 9 8-BIT TIMER H
User’s Manual U16896EJ2V0UD
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9.4 Operation
9.4.1 Operation as interval timer/square wave output
When the count value of 8-bit timer counter Hn and the set value of the CMPn0 register match, an interrupt request
signal (INTTMHn) is generated and 8-bit timer counter Hn is cleared to 00H.
The CMPn1 register cannot be used in the interval timer mode. Even if the CMPn1 register is set, this has no
effect on the timer output because matches between 8-bit timer counter Hn and the CMPn1 register are not detected.
A square wave of the desired frequency (duty = 50%) is output from the TOHn pin, by setting the TMHMDn.TOENn
bit to 1.
Remarks 1.
For the alternate-function pin (TOHn) settings, refer to
Table 4-12 Settings When Port Pins Are
Used for Alternate Functions
.
2.
For INTTMHn interrupt enable, refer to
CHAPTER 17 INTERRUPT/EXCEPTION PROCESSING
FUNCTION
.
Setting
<1> Set each register.
Figure 9-2. Register Settings in Interval Timer Mode
(i) 8-bit timer H mode register n (TMHMDn) settings
0
0/1
0/1
0/1
0
Sets timer output
Sets timer output default level
Sets interval timer mode
Selects count clock (f
CNT
)
Stops count operation
0
0/1
0/1
TMMDn0 TOLEVn
TOENn
CKSHn1
CKSHn2
TMHEn
TMHMDn
CKSHn0 TMMDn1
(ii) CMPn0 register settings
The interval time is as follows if N is set as a comparison value.
•
Interval time = (N + 1)/f
CNT
<2> When the TMHEn bit is set to 1, counting starts.
<3> When the count value of 8-bit timer counter Hn and the set value of the CMPn0 register match, the
INTTMHn signal is generated and 8-bit timer counter Hn is cleared to 00H.
<4> Then, the INTTMHn signal is generated in the same interval. To stop the count operation, clear the TMHEn
bit to 0.
