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Document # 001-20559 Rev. *D
Digital Blocks
17.3
Timing Diagrams
The timing diagrams in this section are presented according to their functionality and are in the following order.
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“Dead Band Timing” on page 200
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“Transmitter Timing” on page 209
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17.3.1
Timer Timing
Enable/Disable Operation.
When the block is disabled,
the clock is immediately gated low. All outputs are gated low,
including the interrupt output. All internal states are reset to
their configuration-specific reset state, except for DR0, DR1,
and DR2 which are unaffected.
Terminal Count/Compare Operation.
In the clock cycle
following the count of 00h, the terminal count (TC) output is
asserted. It is one-half cycle or a full cycle depending on the
TC Pulse Width mode, as set in the block control register. If
this block stands alone or is the least significant block in a
chain, the Carry Out (CO) signal is also asserted. If the
period is set to 00h and the TC Pulse Width mode is one-
half cycle, the output is the inversion of the input clock.
The Compare (CMP) output is asserted in the cycle follow-
ing the compare true and negated one cycle after compare
false.
Multi-Block Terminal Count/Compare Operation.
When
timers are chained, the CO signal of a given block becomes
the Carry In (CI) of the next most significant block in the
chain. In a chained timer, the CO output indicates that block
and all lower blocks are at 00h count. The CO is set up to
the next positive edge of the clock, to enable the next higher
block to count once for every terminal count (TC) of all lower
blocks.
The terminal count out of a given block becomes the termi-
nal count in of the next least significant block in the chain.
The terminal count output indicates that the block and all
higher blocks are at 00h count. The terminal count in/termi-
nal count out chaining signals provide a way for the lower
blocks to know when the upper blocks are at TC. Reload
occurs when all blocks are at TC, which can be determined
by CI, terminal count in, and the block zero detect. Example
timing for a three block timer is shown in
The compare circuit compares registers DR0 <= DR2.
(When Mode[1] = 1, the comparison is DR0 < DR2.)
Each block has an internal compare condition (DR0 com-
pared to DR2), a chaining signal to the next block called
CMPO, and the chaining signal from the previous block
called CMPI. In any given block of a timer, the CMPO is
used to generate the auxiliary output (primary output in the
counter) with a one cycle clock delay.
CMPO is generated from a combination of the internal com-
pare condition and the CMPI input using the following rules:
1. For any given block, if DR0 < DR2, the CMPO condition
is unconditionally asserted.
2. For any given block, if DR0 == DR2, CMPO is asserted
only if the CMPI input to that block is asserted.
3. If the block is a start block, the effective CMPI depends
on the compare type. If it is DR0 <= DR2, the effective
CMPI input is '1'. If it is DR0 < DR2, the effective input is
'0'.
Capture Operation.
In the timer implementation, a rising
edge of the data input or a CPU read of DR0 triggers a syn-
chronous capture event. The result of this is to generate a
latch enable to DR2 that loads the current count from DR0
into DR2. The latch enable signal is synchronized in such a
way that it is not closing near an edge on which the count is
changing.
Содержание PSoC CY8C23533
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