Rev. 1.0, 09/03, page 244 of 568
11.3.1
Timer Counters (TCNT)
Each TCNT is an 8-bit up-counter. TCNT_0 and TCNT_1, or TCNT_2 and TCNT_3 comprise a
single 16-bit register, so they can be accessed together by word access.
This clock source is selected by clock select bits CKS2 to CKS0 in TCR. TCNT can be cleared by
an external reset input signal or compare-match signals A and B. Counter clear bits CCLR1 and
CCLR0 in TCR select the method of clearing.
When TCNT overflows from H
′
FF to H
′
00, the overflow flag (OVF) in TCSR is set to 1.
The initial value of TCNT is H
′
00.
11.3.2
Time Constant Registers A (TCORA)
TCORA is an 8-bit readable/writable register. TCORA_0, TCORA_1, TCORA_2 and TCORA_3
comprise a single 16-bit register, so they can be accessed together by word access.
TCORA is continually compared with the value in TCNT. When a match is detected, the
corresponding compare-match flag A (CMFA) in TCSR is set. Note, however, that comparison is
disabled during the T2 state of a TCORA write cycle.
The timer output from the TMO pin can be freely controlled by the compare-match signal A and
the settings of output select bits OS1 and OS0 in TCSR.
The initial value of TCORA is H
′
FF.
11.3.3
Time Constant Registers B (TCORB)
TCORB is an 8-bit readable/writable register. TCORB_0, TCORB_1, TCORB_2 and TCORB_3
comprise a single 16-bit register, so they can be accessed together by word access.
TCORB is continually compared with the value in TCNT. When a match is detected, the
corresponding compare-match flag B (CMFB) in TCSR is set. Note, however, that comparison is
disabled during the T2 state of a TCORB write cycle.
The timer output from the TMO pin can be freely controlled by the compare-match signal B and
the settings of output select bits OS1 and OS0 in TCSR.
The initial value of TCORB is H
′
FF.
11.3.4
Timer Control Registers (TCR)
TCR selects the TCNT clock source and the time at which TCNT is cleared, and controls interrupt
requests.
Содержание H8S/2627
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