Posted on October 05, 2006 at 06:24Hello,
The first 32 bytes that Neila had talked about are almost always a loop to download more instruction bytes.
Please find below an example of the first 32 bytes received from the ASC0 downloading more code to program the user application:
mov R0, #0FA60h ; R0 is the address to the next byte
W0:
jnb S0RIR, W0 ; wait until a byte is received
movb [R0], S0RBUF ; place the received byte in memory
bclr S0RIR ; clear serial receive flag
movb S0TBUF, [R0] ; transmit (echo) the byte
cmpi1 R0, #(0FA60h+NUMBYTES-1) ; see if all bytes are received
jmpr cc_NE, W0 ; if not repeat
nop
nop
nop
nop
This loop takes exactly 32 bytes to implement. Note that NOP instructions are used to pad the loop to make it exactly 32 bytes. Once the 32-byte loop is received, the microcontroller branches to 0FA40h and starts executing this 32-byte loop. This loop expects more characters to be received and places the received characters in internal memory. After sending the 32-byte loop, more bytes are sent, now to be placed in memory by the loop rather than by the microcontroller’s bootstrap.
This way, when the loop finishes downloading the bytes, execution simply continues, and after the four NOP instructions, the instruction bytes downloaded by the loop are executed.
Regards,
Najoua.
