Motorola DSP56301 user manual Dram Control Register DCR, BRP BRF7 BRF6, BRF3 BRF2 BRF1, BCW0

Bus Interface Unit (BIU) Registers

Table 4-9.Bus Control Register (BCR) Bit Definitions (Continued)

Bit	Bit Name	Reset Value	Description
Number
4–0	BA0W[4–0]	11111	Bus Area 0 Wait State Control
		(31 wait	Defines the number of wait states (one through 31) inserted in each external
		states)	SRAM access to Area 0 (DRAM accesses are not affected by these bits). Area 0 is
			the area defined by AAR0.
			Note: Do not program the value of these bits as zero, since SRAM memory
			access requires at least one wait state.
			When selecting four through seven wait states, one additional wait state is inserted
			at the end of the access. When selecting eight or more wait states, two additional
			wait states are inserted at the end of the access. These trailing wait states increase
			the data hold time and the memory release time and do not increase the memory
			access time.

4.6.2DRAM Control Register (DCR)

The DRAM controller is an efficient interface to dynamic RAM devices in both random read/write cycles and Fast Access mode (Page mode). An on-chip DRAM controller controls the page hit circuit, the address multiplexing (row address and column address), the control signal generation (CAS and RAS) and the refresh access generation (CAS before RAS) for a variety of DRAM module sizes and access times. The on-chip DRAM controller configuration is determined by the DRAM Control Register (DCR). The DRAM Control Register (DCR) is a 24-bit read/write register that controls and configures the external DRAM accesses. The DCR bits are shown in Figure 4-7.

Note: To prevent improper device operation, you must guarantee that all the DCR bits except BSTR are not changed during a DRAM access.

23	22	21	20	19	18	17	16	15	14	13	12
BRP	BRF7	BRF6	BRF5	BRF4	BRF3	BRF2	BRF1	BRF0	BSTR	BREN	BME
11	10	9	8	7	6	5	4	3	2	1	0
BPLE		BPS1	BPS0					BRW1	BRW0	BCW1	BCW0

Reserved bit. Read as zero; write to zero for future compatibility

Figure 4-7.DRAM Control Register (DCR)

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