378
CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
Digital Blocks
shows a detail of the Tx Buffer load timing. The
data bits are shifted out on each of the subsequent clocks.
Following the eighth bit, if parity is enabled, the parity bit is
sent to the output. Finally, the STOP bit is multiplexed into
the data stream. With one-half cycle setup to the next clock,
if new data is available from the TX Buffer register, the next
byte is loaded on the following clock edge and the process is
repeated. If no data is available, a mark (logic 1) is output.
Figure 17-34. Tx Buffer Load Timing
The SCLK (auxiliary) output has a SPI mode 3 clock associ-
ated with the data bits (for the mode 3 timing, see
). During the mark (idle) and framing bits the
SCLK output is high.
Status Generation.
There are two status bits in the Trans-
mitter CR0 register: TX Reg Empty and TX Complete.
TX Reg Empty indicates that a new byte can be written to
the TX Buffer register. When the block is enabled, this status
bit is immediately asserted. This status bit is cleared when
the user writes a byte of data to the TX Buffer register and
set when the data byte in the TX Buffer register is trans-
ferred into the shifter. If a transmission is not already in prog-
ress, the assertion of this signal initiates one subject to the
timing.
The default interrupt in the Transmitter is tied to TX Reg
Empty. However, an initial interrupt is not generated when
the block is enabled. The user must write an initial byte to
the TX Buffer register. That byte must be transferred into the
shifter, before interrupts generated from the TX Reg Empty
status bit are enabled. This prevents an interrupt from occur-
ring immediately on block enable.
TX Complete is an optional interrupt and is generated when
all bits of data and framing bits have been sent. It is cleared
on a read of the CR0 register. This signal may be used to
determine when it is safe to disable the block after data
transmission is complete. In an interrupt driven Transmitter
application, if interrupt on TX Complete is selected, the sta-
tus must be cleared on every interrupt; otherwise, the status
will remain high and no subsequent interrupts are logged.
See
for timing relationships.
Status Clear On Read.
Refer to the SPIM subsection in
.
Figure 17-35. Status Timing for the Transmitter
TXD
IOW
INTERNAL CLOCK
TXREGEMPTY
START
Write is valid on
rising edge of low.
A Tx Buffer write valid in this range will
result in a START bit 1 cycle, after the
subsequent rising edge of the clock.
TX REG EMPTY
TX COMPLETE
Full STOP bit is sent.
CCLK
TXD (F1)
D0
D5
D6
D7
SCLK (F2)
The Shifter is loaded from the TX
Buffer register on this clock edge.
A write to the TX Buffer
register clears this status.
START
STOP
Содержание CY8C28 series
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Страница 85: ...84 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Internal Main Oscillator IMO ...
Страница 93: ...92 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G External Crystal Oscillator ECO ...
Страница 97: ...96 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Phase Locked Loop PLL ...
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Страница 425: ...424 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Analog Reference ...
Страница 461: ...460 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Two Column Limited Analog System ...
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