int e l RESET OPTIONS (VERSION 1.1 ONLY) To Summarize what the user must do to successfully implement a "COLD START" RESET: 1) The user must clear the internal RAM of the MCS BASIC-52 device and at least the first 512 bytes of external RAM memory. 2) The user must initialize the stack pointer (special function register -- SP) and the stack pointer holding register (internal RAM location 3EH) with a value that is between 4DH and 0E0H. 4DH gives MCS BASIC-52 the maximum stack size. 3) The user must initialize the following pointers in external RAM. MTOP at location 10AH (high byte) and 10BH (low byte). VARTOP at locations 104H (high byte) and 105H (low byte).
DIMUSE at locations 108H (high byte) and 109H (low byte). VARUSE at locations 106H (high byte) and 107H (low byte). Details of what needs to be in these locations are presented in appendix 1.7 of this manual. 4) The Control stack pointer (location 11H in internal memory) and the Argument stack pointer (location 09H in internal memory) must also be initialized with the value 0FEH. If the user is not going to assign the XTAL (crystal) value in BASIC, then the XTAL value must be pushed onto the argument stack and the user must Do an OPBYTE 58 call to MCS BASIC-52. 5) The User must also initialize the start address of a program.
The start address is in locations 13H (high byte) and 14H (low byte) of internal data memory. If the user BASIC program is in RAM, then 13H: 14H = 512, if the user program is the the first program in EPROM, then 13H: 14H = 8011H. 6) The user must finally initialize the serial port. Any scheme can be used (as long as it works!!) The added reset options should go a long way toward making MCS BASIC-52 configurable to any custom application. - 152 -