Time Processor Unit 3
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
19-7
Figure 19-3. TCR1 Prescaler Control
19.3.9
Prescaler Control for TCR2
Timer count register 2 (TCR2), like TCR1, is clocked from the output of a prescaler. The T2CG (TCR2
clock/gate control) bit and the T2CSL (TCR2 counter clock edge) bit in TPUMCR determine T2CR2 pin
functions. Refer to
.
The function of the T2CG bit is shown in
When T2CG is set, the external T2CLK pin functions as a gate of the DIV8 clock (the TPU3 system clock
divided by eight). In this case, when the external TCR2 pin is low, the DIV8 clock is blocked, preventing
it from incrementing TCR2. When the external TCR2 pin is high, TCR2 is incremented at the frequency
of the DIV8 clock. When T2CG is cleared, an external clock from the TCR2 pin, which has been
synchronized and fed through a digital filter, increments TCR2. The duration between active edges on the
T2CLK clock pin must be at least nine system clocks.
TPUMCR3[TCR2PSCK2] and TPUMCR[TCR2] determine how the clock source is divided to provide
the output, see
illustrates the TCR2 pre-divider and pre-scaler control.
Table 19-4. TCR2 Counter Clock Source
T2CSL
T2CG
TCR2 Clock
0
0
Rise transition T2CLK
0
1
Gated system clock
1
0
Fall transition T2CLK
1
1
Rise and fall transition T2CLK
System
Prescaler
PSCK
Mux
TCR1
Prescaler
TCR1
DIV2
2,4,6,...64
Prescaler
4, 32
1,2,4,8
EPSCKE
Enhanced
Clock
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...