NEC mPD780851, Preliminary User'S Manual

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CHAPTER 8 8-BIT TIMER/EVENT COUNTERS 2 TM2 AND 3 TM3
Preliminary User’s Manual U14581EJ3V0UM00
8.3 8-Bit Timer/Event Counters 2 TM2 and 3 TM3 Control Registers
The following three types of registers are used to control 8-bit timer/event counters 2 TM2 and 3 TM3.
• Timer clock select registers 2, 3 (TCL2, TCL3)
• 8-bit timer mode control registers 2, 3 (TMC2, TMC3)
• Port mode register 4 (PM4)
(1) Timer clock select registers 2, 3 (TCL2, TCL3)
These registers set count clocks of 8-bit counters 2 and 3 (TM2 and TM3).
TCL2 and TCL3 are set with an 8-bit memory manipulation instruction.
RESET input clears these registers to 00H.
Figure 8-3. Timer Clock Select Register 2 (TCL2) Format
Address: FF74H After Reset: 00H R/W
Symbol 7 6 5 4 3 2 1 0
TCL2 0 0 0 0 0 TCL22 TCL21 TCL20
TCL22 TCL21 TCL20 Count Clock Selection
0 0 0 TIO2 falling edge
0 0 1 TIO2 rising edge
0 1 0 f
X
/2
3
(1.04 MHz)
0 1 1 f
X
/2
5
(261 kHz)
1 0 0 f
X
/2
7
(65.4 kHz)
1 0 1 f
X
/2
8
(32.7 kHz)
1 1 0 f
X
/2
9
(16.3 kHz)
1 1 1 f
X
/2
11
(4.09 kHz)
Cautions 1. When rewriting TCL2 to other data, stop the timer operation beforehand.
2. Bits 3 to 7 must be set to 0.
Remarks 1. f
X
: Main system clock oscillation frequency
2. Figures in parentheses apply to operation with f
X
= 8.38 MHz