Specifications

Factory Masked On-Chip ROM

3-2

3.1 Factory Masked On-Chip ROM

The on-chip ROM in ROM devices is mapped in program memory space. This

ROM is always enabled since these devices lack an external memory inter-

face. This ROM is programmed with customer-specific code.

3.2 Flash

The on-chip flash in flash devices is mapped in program memory space. This

flash memory is always enabled in devices that lack an external memory inter-

face. For the ’2407 which has an external memory interface, the MP/MC

determines whether the on-chip program memory (flash) or the off-chip pro-

gram memory (customer design specific) is accessed.

3.2.1 Flash Control Register Access

In addition to the flash memory array, the flash module has four registers that

control operations on the flash array. At any given time, you can access the

memory array in the flash module (array-access mode) or you can access the

control registers (register-access mode) but you cannot access both simulta-

neously. The flash module has a flash-access control register that selects be-

tween the two access modes. This register is the flash control mode register

(FCMR) and is mapped at FF0Fh in I/O space. This is a special type of I/O reg-

ister that cannot be read. The register functions as follows:

- An OUT instruction, using the register address as an I/O port, places the

flash module in register-access mode. The data operand used is insignifi-

cant. For example:

OUT dummy, 0FF0Fh; Selects register-access mode

- An IN instruction, using the register address as an I/O port, places the flash

module in array-access mode. The data operand used is insignificant. For

example:

IN dummy, 0FF0Fh; Selects array-access mode

The flash array is not directly accessible as memory in register-access mode,

and the control registers are not directly accessible in array-access mode.

When operating as a program memory to store code, the flash module oper-

ates in array-access mode. For details on programming the flash array in

’240x, refer to the

TMS320F20x/F24x DSP Embedded Flash Memory Techni-

cal Reference

(SPRU282).

Factory Masked On-Chip ROM / Flash