Device-Level Timers
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
21-3
Before a timer is enabled to count events, initialize the timer output signal by writing the desired
initialization value to TMRxSCTL[VAL] (page 21-19) and then set the TMRxSCTL[FORC] bit
(page 21-19).
21.1.3 Setting Up Counters for Cascaded Operation
To create a counter larger than 16 bits, the first timer is programmed for the desired configuration
and count mode (it is not programmed in Cascade mode). This first timer also programs the
TMRxCTL[PCS] field to select the desired primary clock. All other timers in the cascade are
simply programmed with their count mode set to Cascade mode (TMRxCTL[CM] = 111). They
also program the TMRxCTL[PCS] field using the appropriate timer N output so that each can
receive their clocks from the previous timer in the chain. The first timer in the chain must never
be programmed in cascade mode. Also, the first timer in the chain must not choose one of the
outputs from the timers for its primary clock. All timers in the cascade follow the counting mode
of the first timer in the chain. In Cascade mode, a special high-speed signal path is used,
bypassing the timer output flag logic to ensure that the cascaded channels operate as a single
synchronous counter. You can connect timers using the other (non-cascade) timer modes and
selecting the outputs of other timers as a clock source. In this case, the timers operate in a ripple
mode, in which higher-order counters transition a clock later than in a purely synchronous design.
This is not the typical use for cascaded counters.
Figure 21-1. Timer Module Block Diagram — One of Four Timers
Prescaler:
/1, /2, /4, ..., /128
CL:ASS64
P
ri
m
a
ry C
loc
k M
U
X
...
Outputs
from Other
MUX
Inputs
Optional
Invert
TMRxSCTL[OPS]
TxSCTL[IPS]
Primary
Secondary
Input
Clock
16-Bit Counter
Load
Clock
Capture
Hold
Compare 1: Up
Compare 2: Down
Internal Bus
Control
Status
Output
Interrupt
Generation
Ov
Cmp1
Cmp2
Optional
Invert
TxSCTL[IPS]
Cmp
1
Cmp
2
Edge
Timer Output
to Primary Clock Multiplex
Timer
Interrupt
TMRxCMPLD1
TMRxCMPLD2
16
C
o
mpar
e
OEN
to
Device
3
of the Other Three Timers
3 Timers
Secondary
Input
Request
Optional
Invert
to
Flag
Other
3 Timers
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...