NEC UPD789026 Series, User Manual

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CHAPTER 6 16-BIT TIMER
User's Manual U11919EJ3V0UM00
99
6.4 16-Bit Timer Operation
6.4.1 Operation as timer interrupt
In the timer interrupt function, interrupts are repeatedly generated at the count value set to 16-bit compare
register 20 (CR20) in advance based on the intervals of the value set in TCL201 and TCL200.
To operate the 16-bit timer as a timer interrupt, the following settings are required.
•
Set count values in CR20
•
Set 16-bit timer mode control register 20 (TMC20) as shown in Figure 6-4.
Figure 6-4. Settings of 16-Bit Timer Mode Control Register 20 at Timer Interrupt Operation
-
0/1 0/1 0/1 0/1 0 0/1 0/1
TOD20 TOF20 CPT201 CPT200 TOC20 TCL201 TCL200 TOE20
TMC20
Setting of Count Clock (see Table 6-2)
Caution If 0 is set both to CPT201 and CPT200 flags, capture edge becomes setting prohibited.
When the count value of 16-bit timer counter 20 (TM20) coincides with the value set to CR20, counting of TM20
continues and an interrupt request signal (INTTM2) is generated.
Table 6-2 shows interval time, and Figure 6-5 shows timing of timer interrupt operation.
Caution Perform the following processing when rewriting CR20 during count operation.
<1> Disable the interrupt (TMMK20 (bit 7 of interrupt mask flag register 0 (MK0)) = 1).
<2> Disable inversion control of timer output data (TOC20 = 0).
If CR20 is rewritten with the interrupt enabled, an interrupt request may be issued
immediately.
Table 6-2. Interval Time of 16-Bit Timer 20
TCL201 TCL200 Count Clock Interval Time
0 0 2
2
/f
X
(0.8
µ
s) 2
18
/f
X
(52.4 ms)
0 1 2
6
/f
X
(12.8
µ
s) 2
22
/f
X
(838.9 ms)
Other than above Setting prohibited
Remarks 1. f
X
: System clock oscillation frequency
2. The parenthesized values apply to operation at f
X
= 5.0 MHz.
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