Tait TB9100, Service Manual, Page: 69 / 132

TB9100 Reciter Service Manual Network Circuitry 69
© Tait Electronics Limited January 2006
read the state of the boot mode selection pins to determine the required
boot load source. Four boot mode selection pins, BOOTM[3..0], specify
the mode in accordance with
Table 5.12 .
In the ASIF, the boot mode pins are strapped through resistor network R402
to select HPI boot mode. In this mode the boot loader does not load any
code but merely jumps to a fixed location (0x10000) in its memory and
executes the pre-loaded code found there.
It is the responsibility of the MPC to pre-load the DSP program code via
the HPI (see
“Host Port Interface (HPI)” on page 69 ). While the MPC is
loading this code, the DSP must not be allowed to start executing this code.
To accomplish this, the DSP incorporates a bit in an HPI control register,
which is cleared by a power-on reset. While this bit is clear the DSP does
not execute its application code. When the MPC has completed loading the
DSP code, it sets this bit in the HPI control register, signaling the DSP to
jump to the start location and execute the loaded program.
5.4.2 Host Port Interface (HPI)
The DSP is connected to the MPC using the Host Port Interface (HPI): this
makes the DSP’s internal memory space accessible as a memory mapped
peripheral in the MPC’s address space. Through the HPI, the MPC has
access to the bottom 1Megaword of the DSP memory space except for the
DSP’s peripheral and control registers. Hence, the MPC accessible memory
includes all of the DARAM and SARAM, plus a portion of the external
DSP memory, if fitted.
Table 5.12 DSP Boot Mode Selection
BOOTM[3..0] Boot Mode
0000 No boot
0001 Serial SPI E2PROM boot from McBSP0 (24-bit addressing)
0010 - 0111 Reserved
1000 No boot
1001 Serial SPI E2PROM boot from McBSP0 (16-bit addressing)
1010 Parallel EMIF boot from 8-bit asynchronous memory
1011 Parallel EMIF boot from 16-bit asynchronous memory
1100 Parallel EMIF boot from 32-bit asynchronous memory
1101 HPI boot
1110 Standard serial boot from McBSP0, 16-bit element length
1111 Standard serial boot from McBSP0, 8-bit element length