M38002M4 Datasheet, PDF (67/173 Pages) Mitsubishi Electric Semiconductor – 8-BIT SINGLE-CHIP MICROCOMPUTER

Control procedure :
Figure 2.2.19 shows a control procedure.
APPLICATION
2.2 Timer
RESET
Initialization
SEI
TM ^{(Address : 2316)}
1110XXXX2
PRE12 ^{(Address : 2016)}
64–1
T1 ^{(Address : 2116)}
8–1
PREY ^{(Address : 2616)}
1–1
TY ^{(Address : 2716)}
256–1
ICON1 ^{(Address : 3E16), bit6} 1
TM ^{(Address : 2316), bit7 0}
CLI
q X : This bit is not used in this application.
Set it to “0” or “1.” It’s value can be disregarded.
q _{All interrupts : Disabled}
q _{Timer Y : Event counter mode}
(Count at falling edge of pulse input from CNTR1 pin)
q _{Set the division ratio so that the Timer 1 interrupt}
occurs every 2 ms.
q _{Timer 1 interrupt : Enabled}
q _{Timer Y count : Start}
q _{Interrupts : Enabled}
Timer 1 interrupt processing routine
CLT (Note 1)
CLD (Note 2)
Push register to stack
1
IREQ1 (Address : 3C 16), bit5?
0
(A)
TY (Address : 27 16)
Note 1: When using the Index X mode flag (T).
Note 2: When using the Decimal mode flag (D).
q _{Push the register used in the interrupt}
processing routine into the stack.
q _{When the count value is 256 or more, the}
processing is performed as out of range.
q _{Read the count value.}
q _{Store the count value in the accumulator (A).}
214 < (A) < 228?
Out of range
Fpulse 0
In range
q _{Compare the count value read with the}
reference value.
q _{Store the comparison result in flag Fpulse.}
Fpulse 1
TY (Address : 2716)
IREQ1 (Address : 3C 16), bit5
256 – 1
0
q _{Initialize the count value.}
q _{Set the Timer Y interrupt request bit to “0.”}
Processing for a result of judgment
Pop registers
q _{Pop registers which is pushed to stack.}
RTI
Fig. 2.2.19 Control procedure [Measurement of frequency]
3800 GROUP USER’S MANUAL
2-19