Motorola MCF5282, MCF5281 user manual Sram Base Address Register Rambar, PRI1 PRI2 SPV, PRI1, PRI2

SRAM Programming Model

5.3.1SRAM Base Address Register (RAMBAR)

The configuration information in the SRAM base address register (RAMBAR) controls the operation of the SRAM module.

•The RAMBAR holds the base address of the SRAM. The MOVEC instruction provides write-only access to this register.

•The RAMBAR can be read or written from the debug module in a similar manner.

•All undefined bits in the register are reserved. These bits are ignored during writes to the RAMBAR, and return zeroes when read from the debug module.

•The RAMBAR valid bit is cleared by reset, disabling the SRAM module. All other bits are unaffected.

The RAMBAR contains several control fields. These fields are shown in Figure 5-1

31		30	29	28	27	26	25	24	23		22	21	20	19	18	17	16
Field	BA31	BA30	BA29	BA28	BA27	BA26	BA25	BA24		BA23	BA22	BA21	BA20	BA19	BA18	BA17	BA16
Reset								Undefined
R/W									W

Field

Reset

R/W Address

15	14	13	12	11	10	9	8		7	6	5	4	3	2	1	0
		—		PRI1	PRI2	SPV		WP		—	C/I	SC	SD	UC	UD	V
						Undefined										0
								W
							CPU + 0xC05

Figure 5-1. SRAM Base Address Register (RAMBAR)

Table 5-1. SRAM Base Address Register

Bits	Name	Description
31–16	BA	Base address. Defines the 0-modulo-64K base address of the SRAM module. By
		programming this field, the SRAM may be located on any 64-Kbyte boundary within the
		processor’s 4-Gbyte address space.
15–12	—	Reserved, should be cleared.
11–10	PRI1, PRI2	Priority bit. PRI1 determines if DMA or CPU has priority in upper 32k bank of memory. PRI2
		determines if DMA or CPU has priority in lower 32k bank of memory. If bit is set, DMA has
		priority. If bit is reset, CPU has priority. Priority is determined according to the following
		table.

	PRI[1:2]	Upper Bank	Lower Bank
		Priority	Priority
	00	DMA Accesses	DMA Accesses
	01	DMA Accesses	CPU Accesses
	10	CPU Accesses	DMA Accesses
	11	CPU Accesses	CPU Accesses
NOTE: The Motorola-recommended setting for the priority bits is 00.

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