Maxim Integrated Secure Microcontroller - Manual (Page 90)

Secure Microcontroller User’s Guide
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the Partition is set to 5800h, the DPTR should be set to 5800h to start. Once data has been saved in NV
RAM, the DPTR should be saved in a known, nonvolatile location so that is can be restored on a reset.
10.3 Interrupts
All interrupts are disabled after a reset so the user must enable individual interrupts as needed, as well as
the global interrupt. Any interrupt needing a higher priority must be selected as such. The following code
example shows the enabling of individual interrupts. A user would combine the appropriate bits as needed
by the application. In this application example, the serial port is given a high priority interrupt.
ORG 00h
SJMP Start
Org
30h
Start :
ORL
PCON, #08h ;Enable Power–fail Warning by setting EPFW
SETB PS ;Set Serial Port Interrupt to High Priority
SETB ES ;Enable Serial Port Interrupt
SETB ET1 ;Enable Timer 1 Interrupt
SETB EX1 ;Enable External Interrupt 1
SETB ET0 ;Enable Timer 0 Interrupt
SETB EX0 ;Enable External Interrupt 0
SETB EA ; Globally enable interrupts
10.4 Timers
The microprocessor disables timer activity (excluding the Watchdog) and serial port communication on a
reset. Therefore, each timer (and serial port, if used) must be reinitialized as part of the reset routine. This
is covered in detail in the User’s Guide section on Timers and Serial I/O respectively. Shown here is an
example of Timer and Serial Port setup. In this example, Timer 0 is set up to generate a 10ms interrupt.
Timer 1 is setup to generate 9600 baud for the serial port. The serial port is set up for asynchronous
communication with a PC (mode 1). A crystal frequency of 11.0592MHz is assumed.
ORG 00h
SJMP Start
Org
30h
Start :
SETB
PS ;Set Serial Port Interrupt to High Priority
SETB ES ;Enable Serial Port Interrupt
SETB ET0 ;Enable Timer 0 Interrupt
MOV TMO, #00100001b ;Select Timer 1 mode 2 – 8 bit auto–reload,
; Timer 0 mode 1 – 16 bit manual reload
MOV TH1, #0FDh ;Setup 9600 baud
MOV TL1, #00h ; ” ”
MOV TH0, #0DBh ;Select a 10 ms count. 9216 counts = 10 ms
MOV TL0, #0FFh ; 9216d counts = 2400h counts (FFFFh–2400h =
; DBFFh)
; Timer 0 ISR must reload DBFFh manually
MOV SCON, #01010011b ;Select Serial Port mode 1,
; TXD and RXD interrupts active
MOV TCON, #01010000b ;Enable the operation of both Timers
SETB EA ;Globally enable interrupts