Motorola DSP56301 - Manual (Page 302)

A -6 DSP56301 User’s Manual
;
;
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; If MD:MC:MB:MA=0100, then it loads the program RAM from a SPI
; compatible Serial EPROM connected to the SCI interface as in the scheme
; below:
;
;
; ___________ __________
; DSP56301 | | SEEPROM
; | |
; SCI(SCLK)|-----------------------|SCK
; | |
; SCI(TXD)|-----------------------|SIN
; | |
; SCI(RXD)|-----------------------|SOUT
; | |
; | |
; | |__
; AA1 |-----------------------|CS
; | |
; ___________| |__________
;
; The SEEPROM is selected by the Address Attribute Pin AA1.
;
; The SCI-SEEPROM bootstrap code expects first to receive 3 bytes
; specifying the number of program words, afterwards 3 bytes
; specifying the address to start loading the program words and
; then 3 bytes for each program word to be loaded. The number of
; words, the starting address and the program words are received
; least significant byte first followed by the mid and then by the most
; significant byte.
;
;
; The program words will be condensed into 24-bit words and
; stored in contiguous PRAM memory locations starting at the
; specified starting address. After the program words are read,
; program execution starts from the same address where loading
; started.
;
; The SCI is configured to work in Mode 0 (8-bit Synchronous), Negative
; Clock Polarity, MSB First Shift Direction. The clock source is
; internal and the SCI frequency is programmed to 1/400 of the chip
; operating frequency
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BOOT equ $D00000 ; this is the location in P memory
; on the external memory bus
; where the external byte-wide
; EPROM would be located
AARV equ $D00409 ; AAR1 selects the EPROM as CE~
; mapped as P from $D00000 to
; $DFFFFF, active low
M_BAAP EQU 2 ; Address Attribute Pin Polarity
M_SSR EQU $FFFF93 ; SCI Status Register
M_STXL EQU $FFFF95 ; SCI Transmit Data Register (low)
M_SRXL EQU $FFFF98 ; SCI Receive Data Register (low)
M_SCCR EQU $FFFF9B ; SCI Clock Control Register
M_SCR EQU $FFFF9C ; SCI Control Register