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DMA Timers (DTIM0–DTIM3)
Freescale Semiconductor
30-8
30.2.6
DMA Timer Counters (DTCN
n
)
The current value of the 32-bit timer counter can be read at anytime without affecting counting. Writes to
DTCN
n
clear the timer counter. The timer counter increments on the clock source rising edge (internal bus
clock divided by 1, internal bus clock divided by 16, or DT
n
IN).
30.3
Functional Description
30.3.1
Prescaler
The prescaler clock input is selected from the internal bus clock (f
sys/2
divided by 1 or 16) or from the
corresponding timer input, DT
n
IN. DT
n
IN is synchronized to the internal bus clock, and the
synchronization delay is between two and three internal bus clocks. The corresponding DTMR
n
[CLK]
selects the clock input source. A programmable prescaler divides the clock input by values from 1 to 256.
The prescaler output is an input to the 32-bit counter, DTCN
n
.
30.3.2
Capture Mode
Each DMA timer has a 32-bit timer capture register (DTCR
n
) that latches the counter value when the
corresponding input capture edge detector senses a defined DT
n
IN transition. The capture edge bits
(DTMR
n
[CE]) select the type of transition that triggers the capture and sets the timer event register capture
event bit, DTER
n
[CAP]. If DTER
n
[CAP] and DTXMR
n
[DMAEN] are set, a DMA request is asserted. If
DTER
n
[CAP] is set and DTXMR
n
[DMAEN] is cleared, an interrupt is asserted.
30.3.3
Reference Compare
Each DMA timer can be configured to count up to a reference value. If the reference value is met,
DTER
n
[REF] is set.
•
If DTMR
n
[ORRI] is set and DTXMR
n
[DMAEN] is cleared, an interrupt is asserted.
•
If DTMR
n
[ORRI] and DTXMR
n
[DMAEN] are set, a DMA request is asserted.
Address:
0x
FC07_00
0C
(
DTCN0
)
0x
FC07_400
C
(
DTCN1
)
0x
FC07_800
C
(
DTCN2
)
0x
FC07_C00
C
(
DTCN3
)
Access: User read/write
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
R
CNT (32-bit timer counter value count)
W
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Figure 30-7. DMA Timer Counters (DTCN
n
)
Table 30-7. DTCN
n
Field Descriptions
Field
Description
31–0
CNT
Timer counter. Can be read at anytime without affecting counting and any write to this field clears it.
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...