AN2153 Freescale Semiconductor / Motorola, AN2153 Datasheet - Page 37

• Manufacturer Part Number: AN2153
• Description: A Serial Bootloader for Reprogramming the MC9S12DP256 FLASH Memory
• Manufacturer: Freescale Semiconductor / Motorola

Secondary Interrupt Vector Jump Table
AN2153
MOTOROLA
The putchar subroutine’s main function is to place a single character,
passed in the B accumulator, into the transmit queue. Once the
character is in the queue and the queue variables have been updated,
the transmit interrupt enable (TIE) bit is set. If transmitter interrupts were
not previously enabled and the transmit data register empty (TDRE) bit
is set, setting the TIE bit will cause an SCI interrupt to occur immediately.
Because the reset and interrupt vectors reside in the protected
bootblock, a secondary vector table is located just below the protected
bootblock area. Each entry in the secondary interrupt table should
consist of a 2-byte address mirroring the primary interrupt and reset
vector table. The secondary interrupt and reset vector table is utilized by
having each vector point to a single JMP instruction that uses the
CPU12’s indexed-indirect program counter relative addressing mode.
This form of the JMP instruction uses four bytes of memory and requires
just six CPU clock cycles to execute. The table in
each vector source with the secondary interrupt table address.
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Secondary Interrupt Vector Jump Table
Figure 14
Application Note
associates
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