TIMER B
8.2 Block description
8.2.1 Counter and Reload register (timer Bi register)
Each of timer Bi counter and reload register consists of 16 bits and has the following functions.
(1) Functions in timer mode and event counter mode
Countdown in the counter is performed each time the count source is input. The reload register is
used to store the initial value of the counter. When a counter underflow occurs, the reload register’s
contents are reloaded into the counter.
A value is set to the counter and reload register by writing the value to the timer Bi register.
Table 8.2.1 lists the memory assignment of the timer Bi register.
The value written into the timer Bi register while counting is not in progress is set to the counter and
reload register. The value written into the timer Bi register while counting is in progress is set only
to the reload register. In this case, the reload register’s updated contents are transferred to the
counter at the next underflow. The counter value is read out by reading out the timer Bi register.
Note: When reading from or writing to the timer Bi register, perform it in a unit of 16 bits. For more
information about the value obtained by reading the timer Bi register, refer to sections
“[Precautions for timer mode]” and “[Precautions for event counter mode].”
(2) Functions in pulse period/pulse width measurement mode
Countup in the counter is performed each time the count source is input. The reload register is used
to retain the pulse period or pulse width measurement result. When a valid edge is input to the TBiIN
pin, the counter value is transferred to the reload register. In this mode, the value obtained by
reading the timer Bi register is the reload register’s contents, so that the measurement result is
obtained.
By using the count-type select bit (bit 4 at addresses 5B16 to 5D16), the count type can be selected
from the counter clear type and free-run type.
The operation of the counter after the counter value is transferred to the reload register is as follows;
• In the case of the counter clear type, the counter value becomes “000016”; and counting continues.
• In the case of the free-run type, the counter value does not become “000016”; and counting continues
with this counter value kept.
Note: When reading from the timer Bi register, perform it in a unit of 16 bits.
Table 8.2.1 Memory assignment of timer Bi registers
High-order byte
Address 5116
Address 5316
Address 5516
Timer Bi register
Timer B0 register
Timer B1 register
Timer B2 register
Low-order byte
Address 5016
Address 5216
Address 5416
Note: At reset, the contents of the timer Bi register
are undefined.
7906 Group User’s Manual Rev.2.0
8-3
RENESAS [ RENESAS TECHNOLOGY CORP ]
