Introduction
The establishment repositions the flag bit to be advantageous for the discrimination different reason initiation the replacement, takes one kind of new technology to accept by more and more new monolithic integrated circuits. For example Philips Corporation’s P87LPC700 and P89LPC900 series, Freescale Corporation (original Motorola semiconductor department) the MC68HC05 series and the MC68HC08 series, Sunplus Corporation’s SPMC65 series, Microchip Corporation’s PIC series and so on, the interior designed has used in recording each kind of replacement symbol specially the condition register.
The MC68HC08 series has a reset state register, is responsible to record 6 kind of replacement flag bits: On electricity replacement, pin replacement, watch-dog replacement, illegal instruction replacement, illegal address replacement and undervoltage replacement. The SPMC65 series has a systems control register, is responsible to record 5 kind of replacement flag bits: On electricity replacement, external reset, watch-dog replacement, illegal address replacement and undervoltage replacement. 51 compatible P89LPC900 series have a replacement source register, is responsible to record 6 kind of replacement flag bits: The undervoltage replacement, on the electricity replacement, the external reset, the watch-dog replacement, the software replacement and UART receive the space character replacement (main achievement to enter one of ISP monitor routine ways). Beginner very commonly used AT89S51/52 and P89C52X2, also additionally built on electricity flag bit POF in its power source control register PCON.
1 repositions the flag bit the establishment method
The traditional 80C51 monolithic integrated circuit does not have the design to reposition the flag bit the logging function, this should say that is one kind of regret, then whether to make up this disappointment through certain technological means? Here provides one kind of enlightenment and the guidance to the general 80C51 monolithic integrated circuit user.
Realizes repositions the flag bit the record definitely to need certain hardware circuit support, but this kind of electric circuit’s design does not have the fixed pattern. The author used piece of MAX813L to design one kind of support electric circuit, as shown in Figure 1, only referred for the reader.
Table 1 user definition system reset symbol register (SRFR)
Table 2 internal may rewrite the memory space replacement situation
