NEC PD754144, PD754244 - page 168

CHAPTER 6 PERIPHERAL HARDWARE FUNCTION
168 User’s Manual U10676EJ3V0UM
(3) Application of CG mode
To use the timer counter as a carrier generator for remote controller signal transmission
The examples shown below apply to the operation of the
µ PD754244 at fX = 4.19 MHz. With fX = 6.0 MHz
operation of the
µ PD754244 and fCC = 1.0 MHz operation of the µ PD754144, the cycles and signal output
periods are different even if the settings are the same.
<1> To generate a carrier clock with a frequency of 38.0 kHz (cycle of 26.3
µ s) and a duty factor of 1/3
•Set the higher 4 bits of the timer counter mode register (TM2) to 0011B and select 61.0
µ s as the
longest set time.
•Set the lower 4 bits of TM2 to 1111B, and select the CG mode and count operation. Then, issue
the timer start command.
•Set the timer counter output enable flag (TOE2) to “1” to enable timer output.
•Set the high-level period setting timer counter modulo register (TMOD2H) as follows.
– 1 = 36.8 – 1 36 = 24H
•The set value of the timer counter modulo register (TMOD2) is as follows.
– 1 = 73.7 – 1 73 = 49H
<Program example>
SEL MB15 ; or CLR1 MBE
MOV XA, #024H
MOV TMOD2H, XA ; Sets modulo (high-level period)
MOV XA, #49H
MOV TMOD2, XA ; Sets modulo (low-level period)
MOV XA, #00111111B
MOV TM2, XA ; Sets mode and starts timer
1 26.3 µ s
3 238 ns
2 26.3 µ s
3 238 ns
.
.