XC908AS60ACFU Motorola Semiconductor Products, XC908AS60ACFU Datasheet - Page 297

• Manufacturer Part Number: XC908AS60ACFU
• Description: MC68HC908AZ60A, MC68HC908AS60A Hcmos Microcontroller Unit Technical Data
• Manufacturer: Motorola Semiconductor Products

19.7 Error Conditions
19.7.1 Overflow Error
MC68HC908AZ60A — Rev 2.0
MOTOROLA
Two flags signal SPI error conditions:
The overflow flag (OVRF in SPSCR) becomes set if the SPI receive data
register still has unread data from a previous transmission when the
capture strobe of bit 1 of the next transmission occurs. (See
3
transferred to the receive data register so that the unread data can still
be read. Therefore, an overflow error always indicates the loss of data.
OVRF generates a receiver/error CPU interrupt request if the error
interrupt enable bit (ERRIE in SPSCR) is also set. MODF and OVRF can
generate a receiver/error CPU interrupt request. (See
not possible to enable only MODF or OVRF to generate a receiver/error
CPU interrupt request. However, leaving MODFEN low prevents MODF
from being set.
If an end-of-block transmission interrupt was meant to pull the MCU out
of wait, having an overflow condition without overflow interrupts enabled
causes the MCU to hang in wait mode. If the OVRF is enabled to
generate an interrupt, it can pull the MCU out of wait mode instead.
If the CPU SPRF interrupt is enabled and the OVRF interrupt is not,
watch for an overflow condition.
miss an overflow.
and
1. Overflow (OVRF in SPSCR) — Failing to read the SPI data
2. Mode fault error (MODF in SPSCR) — The MODF bit indicates
register before the next 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 by accessing the
SPI data register. OVRF is in the SPI status and control register.
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.
Figure
Serial Peripheral Interface (SPI)
19-4.) If an overflow occurs, the data being received is not
Figure 19-6
shows how it is possible to
Serial Peripheral Interface (SPI)
Figure
Error Conditions
Technical Data
Figure 19-
19-8). It is
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