Filter
Top Products
202
CHAPTER 8 8/16-BIT CAPTURE TIMER/COUNTER
■
Program Example of Counter Function
● Processing specifications
• In the 16-bit mode, timer 0 and timer 1 are used to generate an interrupt whenever the external clock to
be input to the EC pin is counted 5,000 times (1388
H
).
• The sample program for reading the 16-bit counter value when the counter is in operation is shown
below (READ16).
● Coding example
DDR3 EQU 000DH ; Address of port 3-direction register
TCCR EQU 0019H ; Address of capture control register
TCR1 EQU 001AH ; Address of timer 1 control register
TCR0 EQU 001BH ; Address of timer 0 control register
TDR1 EQU 001CH ; Address of timer 1 data register
TDR0 EQU 001DH ; Address of timer 0 data register
TIF0 EQU TCR0:7 ; Defines the timer 0 interrupt request flag bit.
ILR1 EQU 007CH ; Address of interrupt level setting register 2
INT_V DSEG ABS ; [DATA SEGMENT]
ORG 0FFF0H
IRQD DW WARI ; Sets the interrupt vector.
ENDS
;------------------------Main program---------------------------------------------------------------------------------
CSEG ; [CODE SEGMENT]
; The stack pointer (SP), etc., is already initialized.
:
MOV DDR3,#00000000B ; Sets the EC pin to input.
CLRI ; Disables the interrupt.
MOV ILR1,#10111111B ; Sets the interrupt level to 2.
MOV TDR0,#088H ; Sets the counter value and the lower 8 bits of the
compare value.
MOV TDR1,#013H ; Sets the counter value and the higher 8 bits of the
compare value.
MOV TCR1,#00001110B ; Sets timer 1 to 16-bit mode.
MOV TCR0,#01101111B ; Clears the timer 0 interrupt request flag, allows interrupt
request output, selects an external clock, clears the
counter, starts the operation, and increments the counter
at a rising edge.
SETI ; Enables a CPU interrupt.
;------------------------Data read subroutine-------------------------------------------------------------------------
READ16
MOVW A,TDR1 ; Reads 16 bits from TDR1 and TDR0.
MOVW A,TDR1 ; Reads 16 bits from TDR1 and TDR0 and stores the old
value in the T register.
CMPW A ; Executes double read check and compares A with T.
BEQ RET16 ; Match and return