Datasheet

DRAM Controller
MOTOROLA MCF5206e USER’S MANUAL 11-43
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Clock H3
The MCF5206e has determined that the external master transfer is a DRAM access, so
the MCF5206e drives A[27:0] with the same value as was registered on the rising edge of
H2. A[27:9] contains the DRAM row address. The MCF5206e also drives DRAMW high,
indicating a DRAM read cycle.
Clock L3
The MCF5206e asserts RAS to indicate the row address is valid on A[27:9].
Clock H4
The MCF5206e internally multiplexes the address and drives out the column address on
A[27:9]. The MCF5206e also actively drives TA negated.
Clock L4
The MCF5206e asserts CAS[0] to indicate the column address is valid on A[27:9]. At this
point the DRAM drives the data on D[31:24].
Clock H5
The MCF5206e asserts the TA signal to indicate that the byte read transfer will be
completed and the read data will be valid on D[31:24] on the next rising edge of CLK.
Clock H6
The MCF5206e then negates RAS, CAS[0], and TA and three-states A[27:0], ending the
byte-read transfer. The negation of RAS starts the RAS precharge. Once A[27:0] has
three-stated, the external master can start another transfer. In this case, the external
master starts a DRAM byte write transfer immediately by driving A[27:0], driving R/W low
indicating a write transfer, driving SIZ[1:0] to $1 indicating a byte transfer, and asserting
TS. The external master must drive the data in the correct byte lanes based on the data
size and the port size of the DRAM, and must drive the data to meet the timing
specifications of the DRAM. In this case, the external master should drive the write data
on D[31:24].
Clock H7
The MCF5206e three-states TA. On the rising edge of CLK where TS is asserted, the
MCF5206e registers the address and attribute signals. The MCF5206e internally decodes
these signals and determines if the external master transfer is a DRAM access. The
external master must three-state A[27:0] after the rising edge of CLK H2, if the internal
address multiplexing is to be used.
Fr
eescale S
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Freescale Semiconductor, Inc.
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