MC908AP32ACFBER Freescale Semiconductor, MC908AP32ACFBER Datasheet - Page 215

• Manufacturer Part Number: MC908AP32ACFBER
• Description: IC MCU 32K FLASH 8MHZ 44-QFP
• Manufacturer: Freescale Semiconductor
• Series: HC08r

Specifications of MC908AP32ACFBER

• Core Processor: HC08
• Core Size: 8-Bit
• Speed: 8MHz
• Connectivity: I²C, IRSCI, SCI, SPI
• Peripherals: LED, LVD, POR, PWM
• Number Of I /o: 32
• Program Memory Size: 32KB (32K x 8)
• Program Memory Type: FLASH
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-QFP
• Processor Series: HC08AP
• Core: HC08
• Data Bus Width: 8 bit
• Data Ram Size: 2 KB
• Interface Type: SCI, SPI
• Maximum Clock Frequency: 8 MHz
• Number Of Programmable I/os: 32
• Number Of Timers: 4
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Development Tools By Supplier: FSICEBASE, DEMO908AP64E, M68CBL05CE
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 8 Channel
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

13.7.1 Overflow Error
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
received after the overflow 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.
OVRF generates a receiver/error CPU interrupt request if the error interrupt enable bit (ERRIE) is also
set. The SPRF, MODF, and OVRF interrupts share the same CPU interrupt vector. (See
It is not possible to enable MODF or OVRF individually to generate a receiver/error CPU interrupt request.
However, leaving MODFEN low prevents MODF from being set.
If the CPU SPRF interrupt is enabled and the OVRF interrupt is not, watch for an overflow condition.
Figure 13-9
possible to read the SPSCR and SPDR to clear the SPRF without problems. However, as illustrated by
the second transmission example, the OVRF bit can be set in between the time that SPSCR and SPDR
are read.
In this case, an overflow can be missed easily. Since no more SPRF interrupts can be generated until this
OVRF is serviced, it is not obvious that bytes are being lost as more transmissions are completed. To
prevent this, either enable the OVRF interrupt or do another read of the SPSCR following the read of the
SPDR. This ensures that the OVRF was not set before the SPRF was cleared and that future
transmissions can set the SPRF bit.
SPSCR read, enable the OVRF to the CPU by setting the ERRIE bit.
Freescale Semiconductor
shows how it is possible to miss an overflow. The first part of
SPSCR
OVRF
READ
READ
SPDR
SPRF
1
2
3
4
BYTE 1
BYTE 1 SETS SPRF BIT.
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS BYTE 1 IN SPDR,
CLEARING SPRF BIT.
BYTE 2 SETS SPRF BIT.
1
2
Figure 13-9. Missed Read of Overflow Condition
3
MC68HC908AP A-Family Data Sheet, Rev. 3
Figure 13-10
BYTE 2
4
Figure 13-4
illustrates this process. Generally, to avoid this second
BYTE 3
5
5
6
7
8
6
and
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST.
CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT,
BUT NOT OVRF BIT.
BYTE 4 FAILS TO SET SPRF BIT BECAUSE
OVRF BIT IS NOT CLEARED. BYTE 4 IS LOST.
7
Figure
13-6.) If an overflow occurs, all data
BYTE 4
8
Figure 13-9
shows how it is
Error Conditions
Figure
13-11.)
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