NEC UPD703116 User Manual page 320

(iv) Mode 4 (PRM1n register's PRM12 = 1, PRM11 = 1, PRM10 = 1)
In mode 4, when two signals out of phase are input to the TIUD1n and TCUD1n pins, up/down
operation is automatically judged and counting is performed according to the timing shown in Figure
9-56.
In mode 4, counting is executed at both the rising and falling edges of the two signals input to the
TIUD1n and TCUD1n pins. Therefore, TM1n counts four times per cycle of an input signal (× 4
count).
TIUD1n
TCUD1n
TM1n
Cautions 1. When mode 4 is specified as the operation mode of TM1n, the valid edge specifications for
pins TIUD1n and TCUD1n are not valid.
2. If the TIUD1n pin edge and TCUD1n pin edge are input simultaneously in mode 4, TM1n
continues the same count operation (up or down) it was performing immediately before the
input.
320
CHAPTER 9 TIMER/COUNTER FUNCTION
Figure 9-56. Mode 4
0003H 0004H 0005H 0006H 0007H
Up count
User's Manual U14492EJ5V0UD
0008H 0009H 000AH 0009H 0008H 0007H 0006H 0005H
Down count