at90ls8535-8mi ATMEL Corporation, at90ls8535-8mi Datasheet - Page 39

• Manufacturer Part Number: at90ls8535-8mi
• Description: 8-bit Microcontroller With 8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

Timer/Counter1 Output
Compare Register – OCR1AH
AND OCR1AL
Timer/Counter1 Output
Compare Register – OCR1BH
AND OCR1BL
1041H–11/01
TEMP, interrupts must be disabled during access from the main program (and from
interrupt routines if interrupts are allowed from within interrupt routines).
•
•
The Timer/Counter1 is realized as an up or up/down (in PWM mode) counter with read
and write access. If Timer/Counter1 is written to and a clock source is selected, the
Timer/Counter1 continues counting in the timer clock cycle after it is preset with the writ-
ten value.
The output compare registers are 16-bit read/write registers.
The Timer/Counter1 Output Compare registers contain the data to be continuously com-
pared with Timer/Counter1. Actions on compare matches are specified in the
Timer/Counter1 Control and Status registers. A compare match only occurs if
Timer/Counter1 counts to the OCR value. A software write that sets TCNT1 and OCR1A
or OCR1B to the same value does not generate a compare match.
A compare match will set the compare interrupt flag in the CPU clock cycle following the
compare event.
Since the Output Compare Registers (OCR1A and OCR1B) are 16-bit registers, a tem-
porary register (TEMP) is used when OCR1A/B are written to ensure that both bytes are
updated simultaneously. When the CPU writes the high byte, OCR1AH or OCR1BH, the
data is temporarily stored in the TEMP register. When the CPU writes the low byte,
Bit
$2B ($4B)
$2A ($4A)
Read/Write
Initial Value
Bit
$29 ($49)
$28 ($48)
Read/Write
Initial Value
TCNT1 Timer/Counter1 Write:
When the CPU writes to the high byte TCNT1H, the written data is placed in the
TEMP register. Next, when the CPU writes the low byte TCNT1L, this byte of data is
combined with the byte data in the TEMP register, and all 16 bits are written to the
TCNT1 Timer/Counter1 register simultaneously. Consequently, the high byte
TCNT1H must be accessed first for a full 16-bit register write operation.
TCNT1 Timer/Counter1 Read:
When the CPU reads the low byte TCNT1L, the data of the low byte TCNT1L is sent
to the CPU and the data of the high byte TCNT1H is placed in the TEMP register.
When the CPU reads the data in the high byte TCNT1H, the CPU receives the data
in the TEMP register. Consequently, the low byte TCNT1L must be accessed first for
a full 16-bit register read operation.
MSB
MSB
R/W
R/W
R/W
R/W
15
15
7
0
0
7
0
0
R/W
R/W
R/W
R/W
14
14
6
0
0
6
0
0
R/W
R/W
R/W
R/W
13
13
5
0
0
5
0
0
R/W
R/W
R/W
R/W
12
12
4
0
0
4
0
0
R/W
R/W
R/W
R/W
11
11
3
0
0
3
0
0
R/W
R/W
R/W
R/W
10
10
2
0
0
2
0
0
AT90S/LS8535
R/W
R/W
R/W
R/W
9
1
0
0
9
1
0
0
LSB
R/W
R/W
LSB
R/W
R/W
8
0
0
0
8
0
0
0
OCR1AH
OCR1BH
OCR1AL
OCR1BL
39