Rev. 1.00, 09/03, page 337 of 704
12.5.4 Cascaded
Operation
In cascaded operation, two 16-bit counters for different channels are used together as a 32-bit
counter.
This function works by counting the channel 1 counter clock at overflow/underflow of TCNT_2 as
set in bits TPSC2 to TPSC0 in TCR.
Underflow occurs only when the lower 16-bit TCNT is in phase counting mode.
Table 12.18 shows the register combinations used in cascaded operation.
Note: When phase counting mode is set for channel 1, the counter clock setting is invalid and the
counter operates independently in phase counting mode.
Table 12.18 Cascaded Combinations
Combination
Upper 16 Bits
Lower 16 Bits
Channels 1 and 2
TCNT_1
TCNT_2
Example of Cascaded Operation Setting Procedure:
Figure 12.21 shows an example of the setting procedure for cascaded operation.
Cascaded operation
Set cascading
Start counting
<Cascaded operation>
Set bits TPSC2 to TPSC0 in the channel 1 TCR
to B'111 to select TCNT_2 overflow/underflow
counting.
Set the CST bit in TSTR for the upper and lower
channel to 1 to start the count operation.
[1]
[2]
[1]
[2]
Figure 12.21 Cascaded Operation Setting Procedure
Examples of Cascaded Operation:
Figure 12.22 illustrates the operation when counting upon TCNT_2 overflow/underflow has been
set for TCNT_1, TGRA_1 and TGRA_2 have been designated as input capture registers, and the
TIOC pin rising edge has been selected.
When a rising edge is input to the TIOCA1 and TIOCA2 pins simultaneously, the upper 16 bits of
the 32-bit data are transferred to TGRA_1, and the lower 16 bits to TGRA_2.
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