TMS320VC5509 datasheet(32/122 Pages) TI

32 / 122 page

Functional Overview

April 2001 − Revised September 2004

SPRS163G

3.1.3 On-Chip Read-Only Memory (ROM)

The one-wait-state ROM is located at the byte address range FF0000h−FFFFFFh. The ROM is composed

of one block of 32K bytes and two 16K-byte blocks, for a total of 64K bytes of ROM. The ROM address space

can be mapped by software to the external memory or to the internal ROM. The 16K ROM blocks at FFC000

to FFFFFF can be configured as secure ROM. (See Section 3.1.4.)

NOTE: Customers can arrange to have the 5509 ROM programmed with contents unique to

any particular application. Contact your local Texas Instruments representative for more

information on custom ROM programming.

The standard 5509 device includes a bootloader program resident in the ROM. When the MPNMC bit field

of the ST3 status register is set through software, the on-chip ROM is disabled and not present in the memory

map, and byte address range FF0000h−FFFFFFh is directed to external memory space. A hardware reset

always clears the MPNMC bit, so it is not possible to disable the ROM at reset. However, the software reset

instruction does not affect the MPNMC bit. All three ROM blocks can be accessed by the program, data, or

DMA buses. The first 16-bit word access to ROM requires three cycles. Subsequent accesses require two

cycles per 16-bit word.

3.1.4 Secure ROM

Included in this 64K-byte ROM is a 16K-byte secure ROM (SROM) that is mapped into the memory space at

reset. This 16K-byte SROM is mapped out of the memory space by writing a “1” to the SROM disable bit field

of the Secure ROM Register (0x7C00) as shown in Figure 3−2. When the SROM disable bit is set, its setting

cannot be changed and the CPU or peripherals cannot access the on-chip SROM memory space. This ROM

block is not programmed on standard 5509 devices, but can be used to implement a custom, secure bootload

feature. Contact your local Texas Instruments representative for more information on custom ROM

programming.

(16K Bytes)

FF0000h

FF8000h

FFC000h

SROM

(If SROM= 0 & MPNMC=0)

FFFFFFh

FF0000h

FF8000h

FFC000h

FFFFFFh

FF0000h

FF8000h

FFC000h

FFFFFFh

ROM

(If MPNMC=0)

ROM

(If MPNMC=0)

External − CE3

(If MPNMC=1)

External − CE3

(If MPNMC=1)

External − CE3

(If MPNMC=1)

ROM

(If MPNMC=0)

ROM

(If MPNMC=0)

SROM=0

SROM=1

SROM

Secure ROM Register

No access

(If SROM=1 & MPNMC=0)

Byte

Address

Byte

Address

Byte

Address

(32K Bytes)

(16K Bytes)

(32K Bytes)

(16K Bytes)

Figure 3−2. Secure ROM

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