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Document # 001-20559 Rev. *D
Digital Blocks
17.3.7
SPIS Timing
Enable/Disable Operation.
As soon as the block is config-
ured for SPI slave and before enabling, the MISO output is
set to idle at logic 1. Both the enable bit must be set and the
SS_ asserted (either driven externally or forced by firmware
programming) for the block to output data. When enabled,
the primary output is the MSb or LSb of the shift register,
depending on the LSb First configuration in bit 7 of the con-
trol register. The auxiliary output of the SPIS is always
forced into tri-state.
Since the SPIS has no internal clock, it must be enabled
with set up time to any external master supplying the clock.
Set up time is also required for a TX Buffer register write,
before the first edge of the clock or the first falling edge of
SS_, depending on the mode. This set up time must be
assured through the protocol and an understanding of the
timing between the master and slave in a system.
When the block is disabled, the MISO output reverts to its
idle '1' state. All internal states are reset (including CR0 sta-
tus) to their configuration-specific reset state, except for
DR0, DR1, and DR2, which are unaffected.
Normal Operation.
Typical timing for an SPIS transfer is
. If the SPIS is pri-
marily being used as a receiver, the RX Reg Full (polling
only) or SPI Complete (polling or interrupt) status may be
used to determine when a byte has been received. In this
way, the SPIS operates identically to the SPIM. However,
there are two main areas in which the SPIS operates differ-
ently: 1) SPIS behavior related to the SS_ signal, and 2) TX
data queuing (loading the TX Buffer register).
Figure 17-20. Typical SPIS Timing in Modes 0 and 1
SCLK (internal)
TX REG EMPTY
D7
MISO
D6
D5
D2
D1
D0
User writes first byte to the
TX Buffer register in
advance of transfer.
At the falling edge of SS_, MISO
transitions from an IDLE (high)
to output the first bit of data.
User writes the next byte
to the TX Buffer register.
SCLK (MODE 0)
Last bit of received data is valid
on this edge and is latched into
the RX Buffer register.
SCLK (MODE 1)
SS_
RX REG FULL
First input
bit is
latched.
First
Shift
D7
D6
D7
Содержание PSoC CY8C23533
Страница 4: ...Contents Overview 4 Document 001 20559 Rev D Section G Glossary 385 Index 401 ...
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Страница 24: ...24 Document 001 20559 Rev D Section A Overview ...
Страница 30: ...30 Document 001 20559 Rev D Pin Information ...
Страница 54: ...54 Document 001 20559 Rev D Supervisory ROM SROM ...
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Страница 68: ...68 Document 001 20559 Rev D Interrupt Controller ...
Страница 76: ...12 Document 001 20559 Rev D General Purpose IO GPIO ...
Страница 82: ...18 Document 001 20559 Rev D Internal Main Oscillator IMO ...
Страница 84: ...20 Document 001 20559 Rev D Internal Low Speed Oscillator ILO ...
Страница 90: ...26 Document 001 20559 Rev D External Crystal Oscillator ECO ...
Страница 94: ...30 Document 001 20559 Rev D Phase Locked Loop PLL ...
Страница 106: ...42 Document 001 20559 Rev D Sleep and Watchdog ...
Страница 228: ...164 Document 001 20559 Rev D Section D Digital System ...
Страница 234: ...170 Document 001 20559 Rev D Array Digital Interconnect ADI ...
Страница 278: ...214 Document 001 20559 Rev D Digital Blocks ...
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Страница 308: ...244 Document 001 20559 Rev D Analog Input Configuration ...
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