MC68HC708XL36 FREESCALE [Freescale Semiconductor, Inc], MC68HC708XL36 Datasheet - Page 214

• Manufacturer Part Number: MC68HC708XL36
• Description: HCMOS Microcontroller Unit
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

SPI
Error Conditions
Overflow Error
MC68HC708XL36
214
For an idle master or idle slave that has no data loaded into its transmit
buffer, the SPTE is set again no more than two bus cycles after the
transmit buffer empties into the shift register. This allows the user to
queue up a 16-bit value to send. For an already active slave, the load of
the shift register cannot occur until the transmission is completed. This
implies that a back-to-back write to the transmit data register is not
possible. The SPTE indicates when the next write can occur.
The following flags signal SPI error conditions:
The overflow flag (OVRF) becomes set if the receive data register still
has unread data from a previous transmission when the capture strobe
of bit 1 of the next transmission occurs. The bit 1 capture strobe occurs
in the middle of SPSCK cycle 7. (See
6
and before the OVRF bit is cleared does not transfer to the receive data
register and does not set the SPI receiver full bit (SPRF). The unread
data that transferred to the receive data register before the overflow
occurred can still be read. Therefore, an overflow error always indicates
the loss of data. Clear the overflow flag by reading the SPI status and
control register and then reading the SPI data register.
on page 210.) If an overflow occurs, all data received after the overflow
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Overflow (OVRF) — Failing to read the SPI data register before
the next full byte enters the shift register sets the OVRF bit. The
new byte does not transfer to the receive data register, and the
unread byte still can be read. OVRF is in the SPI status and control
register.
Mode fault error (MODF) — The MODF bit indicates that the
voltage on the slave select pin (SS) is inconsistent with the mode
of the SPI. MODF is in the SPI status and control register.
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SPI
Figure 4
on page 209 and
MOTOROLA
Figure
14-spi_c