SN8F2280 Series
USB 2.0 Full-Speed 8-Bit Micro-Controller
8.4.4 TCnR AUTO-LOAD REGISTER
TCn (n = 0, 1, 2) timer is with auto-load function controlled by ALOADn (n = 0, 1, 2) bit of TCnM (n = 0, 1, 2). When
TCnC (n = 0, 1, 2) overflow occurring, TCnR (n = 0, 1, 2) value will load to TCnC by system. It is easy to generate an
accurate time, and users don’t reset TCnC during interrupt service routine.
TCn is double buffer design. If new TCnR value is set by program, the new value is stored in 1st buffer. Until TCn
overflow occurs, the new value moves to real TCnR buffer. This way can avoid TCn interval time error and glitch in
PWM and Buzzer output.
Note: Under PWM mode, auto-load is enabled automatically. The ALOADn bit is selecting overflow
boundary.
08AH
TC0R
Read/Write
After reset
Bit 7
TC0R7
W
Bit 6
TC0R6
W
Bit 5
TC0R5
W
Bit 4
TC0R4
W
Bit 3
TC0R3
W
Bit 2
TC0R2
W
Bit 1
TC0R1
W
Bit 0
TC0R0
W
0
0
0
0
0
0
0
0
08DH
TC1R
Read/Write
After reset
Bit 7
TC1R7
W
Bit 6
TC1R6
W
Bit 5
TC1R5
W
Bit 4
TC1R4
W
Bit 3
TC1R3
W
Bit 2
TC1R2
W
Bit 1
TC1R1
W
Bit 0
TC1R0
W
0
0
0
0
0
0
0
0
090H
TC2R
Read/Write
After reset
Bit 7
TC2R7
W
Bit 6
TC2R6
W
Bit 5
TC2R5
W
Bit 4
TC2R4
W
Bit 3
TC2R3
W
Bit 2
TC2R2
W
Bit 1
TC2R1
W
Bit 0
TC2R0
W
0
0
0
0
0
0
0
0
The equation of TCnR initial value is as following.
TCnR initial value = N - (TCn interrupt interval time * input clock)
N is TCn overflow boundary number. TCn timer overflow time has six types (TCn timer, TCn event counter, TCn Fcpu
clock source, TCn Fosc clock source, PWM mode and no PWM mode). These parameters decide TCn overflow time
and valid value as follow table.
TCnR valid
value
TCnR value
binary type
TCnCKS PWMn ALOADn TCnOUT
N
0
1
1
1
1
-
x
0
0
1
1
-
x
0
1
0
1
-
256
256
64
32
16
0x00~0xFF 00000000b~11111111b
0x00~0xFF 00000000b~11111111b
0
1
0x00~0x3F
0x00~0x1F
0x00~0x0F
xx000000b~xx111111b
xxx00000b~xxx11111b
xxxx0000b~xxxx1111b
256
0x00~0xFF 00000000b~11111111b
¾
Example: To set 1ms interval time for TCn interrupt. TCn clock source is Fcpu (TCnKS=0) and no PWM
output (PWMn=0). High clock is internal 6MHz. Fcpu=Fosc/2. Select TCnRATE=010 (Fcpu/64).
TCnR initial value = N - (TCn interrupt interval time * input clock)
= 256 - (1ms * 6MHz / 1 / 64)
= 256 - (10-3 * 6 * 106 / 1 / 64)
= 162
= A2H
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