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MC68340 データシート(PDF) 82 Page - Freescale Semiconductor, Inc |
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MC68340 データシート(HTML) 82 Page - Freescale Semiconductor, Inc |
82 / 441 page MOTOROLA MC68340 USER’S MANUAL 3- 33 EXAMPLE B: A system uses error detection and correction on RAM contents. The designer may: 1. Delay DSACK ≈ until data is verified and assert BERR and HALT simultaneously to indicate to the MC68340 to automatically retry the error cycle (case 5), or if data is valid, assert DSACK ≈ (case 1). 2. Delay DSACK ≈ until data is verified and assert BERR with or without DSACK≈ if data is in error (case 3). This initiates exception processing for software handling of the condition. 3. Return DSACK ≈ prior to data verification; if data is invalid, BERR is asserted on the next clock cycle (case 4). This initiates exception processing for software handling of the condition. 4. Return DSACK ≈ prior to data verification; if data is invalid, assert BERR and HALT on the next clock cycle (case 6). The memory controller can then correct the RAM prior to or during the automatic retry. Table 3-4. DSACK ≈, BERR, and HALT Assertion Results Asserted on Rising Edge of State Case Num Control Signal N N + 2 Result 1 DSACK ≈ BERR HALT A NA NA S NA X Normal cycle terminate and continue. 2 DSACK ≈ BERR HALT A NA A/S S NA S Normal cycle terminate and halt; continue when HALT negated. 3 DSACK ≈ BERR HALT NA/A A NA X S X Terminate and take bus error exception, possibly deferred. 4 DSACK ≈ BERR HALT A NA NA X A NA Terminate and take bus error exception, possibly deferred. 5 DSACK ≈ BERR HALT NA/A A A/S X S S Terminate and retry when HALT negated. 6 DSACK ≈ BERR HALT A NA NA X A A Terminate and retry when HALT negated. NOTES: N — Number of the current even bus state (e.g., S2, S4, etc.) A — Signal is asserted in this bus state NA — Signal is not asserted in this state X — Don't care S — Signal was asserted in previous state and remains asserted in this state Freescale Semiconductor, Inc. For More Information On This Product, Go to: www.freescale.com |
同様の部品番号 - MC68340 |
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同様の説明 - MC68340 |
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