CHAPTER 4 BCU
Preliminary User’s Manual A14874EJ3V0UM
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(3) Byte enable
The bus master uses the VMBENZ3 to VMBENZ0 signals to indicate the byte data among the data obtained by
quartering the data bus (VBDI31 to VBDI0 and VBDO31 to VBDO0) into byte units.
Table 4-3. VMBENZ3 to VMBENZ0 Signals
Active (Low-Level Output) Signal
Enabled Byte Data
VMBENZ0
VBDI7 to VBDI0, VBDO7 to VBDO0
VMBENZ1
VBDI15 to VBDI8, VBDO15 to VBDO8
VMBENZ2
VBDI23 to VBDI16, VBDO23 to VBDO16
VMBENZ3
VBDI31 to VBDI24, VBDO31 to VBDO24
(4) Transfer size
The bus master uses the VMSIZE1 and VMSIZE0 signals to indicate the transfer size.
Table 4-4. VMSIZE1 and VMSIZE0 Signals
VMSIZE1
VMSIZE0
Explanation
0
0
Byte (8 bits)
0
1
Halfword (16 bits)
1
0
Word (32 bits)
1
1
(Reserved for future function expansion)
Remark
0: low-level 1: high-level
(5) Sequential status
The bus master uses the VMSEQ2 to VMSEQ0 signals to indicate the “burst transfer length” when a burst
transfer starts, to indicate “continuous” during a burst transfer, and to indicate “single transfer” at the end of the
burst transfer.
Table 4-5. VMSEQ2 to VMSEQ0 Signals
VMSEQ2
VMSEQ1
VMSEQ0
Sequential Status
0
0
0
Single transfer
0
0
1
Continuous (indicates that the next transfer address is related to the current
transfer address)
Note
0
1
0
Continuous 4 times (burst transfer length: 4)
0
1
1
Continuous 8 times (burst transfer length: 8)
1
0
0
Continuous 16 times (burst transfer length: 16)
1
0
1
Continuous 32 times (burst transfer length: 32)
1
1
0
Continuous 64 times (burst transfer length: 64)
1
1
1
Continuous 128 times (burst transfer length: 128)
Note
This is output during continuous 2 times, or continuous 4, 8, 16, 32, 64, or 128 times transfer.
Remark
0: low-level 1: high-level
