NEC 78K0 User Manual page 181

(4) Prescaler mode register 0n (PRM0n)
This register is used to set the 16-bit timer counter 0n (TM0n) count clock and TI00n and TI01n input valid edges.
PRM0n can be set by a 1-bit or 8-bit memory manipulation instruction.
RESET input clears PRM0n to 00H.
µ
Remark n = 0: PD780143, 780144
µ
n = 0, 1: PD780146, 780148, 78F0148
CHAPTER 7 16-BIT TIMER/EVENT COUNTERS 00 AND 01
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User's Manual U15947EJ2V0UD
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