データシートサーチシステム |
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MC68340 データシート(PDF) 56 Page - Freescale Semiconductor, Inc |
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MC68340 データシート(HTML) 56 Page - Freescale Semiconductor, Inc |
56 / 441 page MOTOROLA MC68340 USER’S MANUAL 3- 7 OP1 OP0 OP0 OP2 OP1 OP0 OP3 OP2 OP1 OP0 31 23 15 70 D0 D8 D15 D7 OP0 OP0 (OP0) OP0 OP0 (OP0) (OP0) OP0 (OP1) OP1 OP0 (OP1) OP0 OP1 A0 SIZ0 SIZ1 Case (a) (b) (c) (d) (e) (f) (g) 01 X 10 0100 X 0110 X 10010 1000 X 00010 0000 X Transfer Case Byte to Byte Byte to Word (Even) Byte to Word (Odd) Word to Byte (Aligned) Word to Word (Aligned) Long Word to Byte (Aligned) Long Word to Word (Aligned) OPERAND Data Bus DSACK0 DSACK1 NOTES: 1. Operands in parentheses are ignored by the MC68340 during read cycles. 2. A 3-byte to byte transfer does occur as the second byte transfer of a long-word to byte port transfer. Figure 3-2. MC68340 Interface to Various Port Sizes 3.2.2 Misaligned Operands In this architecture, the basic operand size is 16 bits. Operand misalignment refers to whether an operand is aligned on a word boundary or overlaps the word boundary, determined by address line A0. When A0 is low, the address is even and is a word and byte boundary. When A0 is high, the address is odd and is a byte boundary only. A byte operand is properly aligned at any address; a word or long-word operand is misaligned at an odd address. At most, each bus cycle can transfer a word of data aligned on a word boundary. If the MC68340 transfers a long-word operand over a 16-bit port, the most significant operand word is transferred on the first bus cycle, and the least significant operand word is transferred on a following bus cycle. The CPU32 restricts all operands (both data and instructions) to be aligned. That is, word and long-word operands must be located on a word or long-word boundary, respectively. The only type of transfer that can be performed to an odd address is a single-byte transfer, referred to as an odd-byte transfer. If a misaligned access is attempted, the CPU32 generates an address error exception, and enters exception processing. Refer to Section 5 CPU32 for more information on exception processing. 3.2.3 Operand Transfer Cases The following cases are examples of the allowable alignments of operands to ports. 3.2.3.1 BYTE OPERAND TO 8-BIT PORT, ODD OR EVEN (A0 = X). The MC68340 drives the address bus with the desired address and the SIZx pins to indicate a single- byte operand. 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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