TMS320LF2401A_09 Datasheet, PDF (35/88 Pages) Texas Instruments – DSP CONTROLLERS

TMS320LF2401A, TMS320LC2401A
DSP CONTROLLERS
SPRS161K − MARCH 2001 − REVISED JULY 2007
boot ROM^†
Boot ROM is a 256-word ROM mapped in program space 0000h−00FFh. This ROM will be enabled if the
BOOT_EN mode is enabled during reset. Boot-enable function is implemented using combinational logic of the
TDI, TRST, and RS pins as described below. The on-chip bootloader is invoked when:
TRST
=0
RS
=0
TDI
=0
(In addition to the three pins mentioned above, the application must ensure that PDPINTA stays high during the
execution of the boot ROM code.) Since it has an internal pulldown, the TRST pin will be low, provided the JTAG
connector is not connected. Therefore, the BOOT_EN bit (bit 3 of the SCSR2 register) will be set to 0 if TDI is
low upon reset. If on-chip bootloader is desired while debugging with the JTAG connector connected
(TRST = 1), it can be achieved by writing a “0” into bit 3 of the SCSR2 register.
The boot ROM has a generic bootloader to transfer code through the SCI port. The incoming code should
disable the BOOT_ROM bit by writing 1 to bit 3 of the SCSR2 register, or else, the whole Flash array will not
be enabled.
The boot ROM code sets the PLL to x2 or x4 option based on the condition of the SCITXD pin during reset. The
SCITXD pin should be pulled high/low to select the PLL multiplication factor. The choices made are as follows:
D If the SCITXD pin is pulled low, the PLL multiplier is set to 2.
D If the SCITXD pin is pulled high, the PLL multiplier is set to 4. (Default)
D If the SCITXD pin is not driven at reset, the internal pullup selects the default multiplier of 4.
Care should be taken such that a combination of CLKIN and the PLL multiplication factor does not result in a
CPU clock speed of greater than 40 MHz, the maximum rated speed. For restrictions concerning the maximum
frequency of CLKIN, see the latest revision of the TMS320LF2401A DSP Controller Silicon Errata (literature
number SPRZ013).
Furthermore, when the bootloader is used, only specific values of CLKIN would result in a baud-lock for the SCI.
Refer to the TMS320LF/LC240xA DSP Controllers Reference Guide: System and Peripherals (literature
number SPRU357) for more details about the bootloader operation.
† _{The boot ROM on LC2401A is used for test purposes.}
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