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First let me describe a little bit about our system:
It is not von-neuman, and the main code executes from OTP (One Time Programable) memory. there is also a small amount of XRAM, and code can also be executed from there too.
When executing from OTP, we are unable to use MOVX to read or write CODE. We can use MOVC read CODE.
When executing from XRAM, we are unable to use MOVX to read or write XDATA. We can use both MOVC and MOVX to read CODE.
Despite being OTP, we do have the ability to dynamically patch an small number of quads of OTP code at any address to whatever value we choose.
My belief is that all the elements that are needed to execute a MON51 stub from OTP are present. We can patch code to jump to the stub on a break point, and code can be read through the MOVC to keep adjacent instructions coherent in the patch?
My question is, does anyone have any experience or deep working knowledege of the MON51 that can point me to section that inserts the jumps that set and clear break points? Are there any thoughts about how to modify this with minimum impact on the stub?
Thanks in advance,
Chris.
All you need to do for implementing MON51 is providing the functions that are described at the end of INSTALL.A51:
;******************************************************************** ;* Interface via standard 8051 UART * ;******************************************************************** SER_INT_ADR EQU 23H ; ADDRESS OF SERIAL INTERRUPT VECTOR SER_INT_ADR_OFF EQU (INT_ADR_OFF + SER_INT_ADR) INSTAT: MOV C,RI ; INPUT STATUS OF SERIAL INTERFACE RET OUTSTAT: MOV C,TI ; OUTPUT STATUS OF SERIAL INTERFACE RET INCHAR: MOV A,SBUF ; CHARACTER INPUT-ROUTINE RET OUTCHAR: MOV SBUF,A ; CHARACTER OUTPUT-ROUTINE RET CLR_TI: CLR TI ; CLEAR SERIAL TRANSMIT INTERRUPT FLAG RET SET_TI: SETB TI ; SET SERIAL TRANSMIT INTERRUPT FLAG RET CLR_RI: CLR RI ; CLEAR SERIAL RECEIVE INTERRUPT FLAG RET CLR_SER_IE: CLR ES ; CLEAR SERIAL INTERRUPT ENABLE FLAG RET SET_SER_IE: SETB ES ; SET SERIAL INTERRUPT ENABLE FLAG RET BEFORE_GO: ; this code is executed before a RET ; a go or proc step is executed AFTER_GO: ; this code is executed after a go RET ; command (when a breakpoint was set) WR_CODE: MOVX @DPTR,A ; insert different code here, but RET ; do not change any other register ; without saving it
So you are correct, MON51 is very flexible (and the variant of it FlashMON51 is maybe even more flexible).