NEC PD789860 User Manual page 87

Figure 9-3. Block Diagram of Output Controller (Timer 40)
TOE40 RMC40
F/F
(1) 8-bit compare register 30 (CR30)
This register is an 8-bit register that always compares the count value of 8-bit timer counter 30 (TM30) with
the value set in CR30 and generates an interrupt request (INTTM30) if they match.
CR30 is set with an 8-bit memory manipulation instruction.
RESET input makes this register undefined.
Caution CR30 cannot be used in PWM output mode.
(2) 8-bit compare register 40 (CR40)
This register is an 8-bit register that always compares the count value of 8-bit timer counter 40 (TM40) with
the value set in CR40 and generates an interrupt request (INTTM40) if they match. In addition, when
cascade-connected to TM30 and used as a 16-bit timer/event counter, an interrupt request (INTTM40) is
generated only if TM30 matches with CR30 and TM40 matches with CR40 simultaneously (INTTM30 is not
generated).
In carrier generator mode or PWM output mode, set the low-level width of the timer output.
CR40 is set with an 8-bit memory manipulation instruction.
RESET input makes this register undefined.
(3) 8-bit compare register H40 (CRH40)
In carrier generator mode or PWM output mode, writing a CRH40 value sets the width of high level timer
output.
The value set in CRH40 is constantly compared with the TM40 count value, and an interrupt request
(INTTM40) is generated if they match.
CRH40 is set with an 8-bit memory manipulation instruction.
RESET input makes this register undefined.
(4) 8-bit timer counters 30 and 40 (TM30, TM40)
These 8-bit registers count pulse counts.
Each of TM30 and TM40 is read with an 8-bit memory manipulation instruction.
RESET input clears these registers to 00H.
The conditions under which TM30 and TM40 are cleared to 00H are shown next.
CHAPTER 9 8-BIT TIMERS 30 AND 40
NRZ40
Carrier generator mode
User's Manual U14826EJ5V0UD
P20
PM20
output latch
TMO/P20/
BSFO
Carrier clock
87