DSP56857 datasheet(134/662 Pages) FREESCALE

134 / 662 page

5685X Digital Signal Controller User Manual, Rev. 4

5-8

Freescale Semiconductor

the base address can be at block size boundaries only). For example, for a block size of 64k, the

base address can be 64k, 128k, 192k, 256k, 320k, etc.

Note:

The default reset value for CSn will enable a 32K block of external memory starting at

address zero. This may be defined to be something else for a specific chip in which

case the chip user manual will detail the specific reset value.

Figure 5-3. Chip Select Base Address Registers 0–3 (CSBAR0–CSBAR3)

See Programmer’s Sheet on Appendix page B-9

5.6.2 Chip Select Option Registers 0–3 (CSOR0–CSOR3)

A Chip Select Option Register is required for every chip select. This register specifies the mode

of operation of the chip select and the timing requirements of the external memory.

Note:

The CSn logic can be used to define external memory wait states even if the CSn pin is

used as GPIO.

Note:

The CSn output can be disabled by setting either the PS/DS, R/W or BYTE_EN fields

to zero.

Base + $0 - $3

Read

ADR23 ADR22 ADR21 ADR20 ADR19 ADR18 ADR17 ADR16 ADR15 ADR14 ADR13 ADR12

BLKSZ

Write

Reset

000

0000

000

Table 5-2. CSBAR Encoding of the BLKSZ Field

BLKSZ

Block Size

Address Lines Compared

0000

X: ADR[23:12], P: ADR[20:12]

0001

X: ADR[23:13], P: ADR[20:13]

0010

16K

X: ADR[23:14], P: ADR[20:14]

0011

32K

X: ADR[23:15], P: ADR[20:15]

0100

64K

X: ADR[23:16], P: ADR [20:16]

0101

128K

X: ADR[23:17], P: ADR[20:17]

0110

256K

X: ADR[23:18], P: ADR[20:18]

0111

512K

X: ADR[23:19], P: ADR [20:19]

1000

X: ADR[23:20], P: ADR[20:20]

1001

X: ADR[23:21]. All program address space decoded.

1010

X: ADR[23:22]. No program address space decoded.

1011

X: ADR[23:23]. No program address space decoded.

1100

16M

All data address space decoded. No program address space decoded.

1101

Reserved

No data address space decoded. No program address space decoded.

1110

Reserved

No data address space decoded. No program address space decoded.

1111

Reserved

No data address space decoded. No program address space decoded.

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