MC68340AG16E Freescale Semiconductor, MC68340AG16E Datasheet - Page 83

• Manufacturer Part Number: MC68340AG16E
• Description: IC MPU 32BIT 16MHZ 144-LQFP
• Manufacturer: Freescale Semiconductor

Specifications of MC68340AG16E

• Processor Type: M683xx 32-Bit
• Speed: 16MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 144-LQFP
• Controller Family/series: 68K
• Core Size: 32 Bit
• No. Of I/o's: 16
• Cpu Speed: 16MHz
• No. Of Timers: 2
• Embedded Interface Type: UART
• Digital Ic Case Style: LQFP
• Rohs Compliant: Yes
• Processor Series: M683xx
• Core: CPU32
• Maximum Clock Frequency: 16 MHz
• Maximum Operating Temperature: + 105 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Lead Free Status / Rohs Status: Details

3.5.1 Bus Errors
BERR can be used to abort the bus cycle and the instruction being executed. BERR takes
precedence over DSACK provided it meets the timing constraints described in Section
11 Electrical Characteristics. If BERR does not meet these constraints, it may cause
unpredictable operation of the MC68340. If BERR remains asserted into the next bus
cycle, it may cause incorrect operation of that cycle. When BERR is issued to terminate a
bus cycle, the MC68340 can enter exception processing immediately following the bus
cycle, or it can defer processing the exception.
The instruction prefetch mechanism requests instruction words from the bus controller
before it is ready to execute them. If a bus error occurs on an instruction fetch, the
MC68340 does not take the exception until it attempts to use that instruction word. Should
an intervening instruction cause a branch or should a task switch occur, the bus error
exception does not occur. The bus error condition is recognized during a bus cycle in any
of the following cases:
When the MC68340 recognizes a bus error condition, it terminates the current bus cycle in
the normal way. Figure 3-17 shows the timing of a bus error for the case in which
DSACK is not asserted. Figure 3-18 shows the timing for a bus error that is asserted
after DSACK . Exceptions are taken in both cases. Refer to Section 5 CPU32 for details
of bus error exception processing.
In the second case, in which BERR is asserted after DSACK is asserted, BERR must be
asserted within the time specified for purely asynchronous operation, or it must be
asserted and remain stable during the sample window around the next falling edge of the
clock after DSACK is recognized. If BERR is not stable at this time, the MC68340 may
exhibit erratic behavior. BERR has priority over DSACK . In this case, data may be
present on the bus, but it may not be valid. This sequence can be used by systems that
have memory error detection and correction logic and by external cache memories.
3-34
• DSACK and HALT are negated, and BERR is asserted.
• HALT and BERR are negated, and DSACK is asserted. BERR is then asserted
• BERR and HALT are asserted simultaneously, indicating a retry.
within one clock cycle ( HALT remains negated).
Freescale Semiconductor, Inc.
For More Information On This Product,
MC68340 USER’S MANUAL
Go to: www.freescale.com
MOTOROLA