EM77950
BB Controller
11.3 PWM Programming Procedures/Steps
(1) Load PRDX with the PWMX period.
(2) Load DTX with the PWMX Duty Cycle.
(3) Enable the interrupt function by setting PWMXIE in the INTE register, if required.
(4) Set the PWM pin as output by setting PWMCR.S_PWMX.
(5) Enable the PWM function by setting PWMXE bit in the PRIE register.
(6) Write the desired new duty to DTX before TMRX is equal to PRDX, then this new
DTX will be latched into DLX if various duty cycle is required for the next PWMX
operation.
(7) Clear PWMXE bit and write the desired new period to PRDX, then enable it again if
various periods are required for the next PWMX operation.
(8) Clear the PWMXIF before the next operation if interrupt PWMXIE is employed.
12 Interrupts
12.1 Introduction
The EM77950 has 15 interrupt sources. By priority, these interrupts are classified into
two levels, namely; peripherals and base band, as described in the following:
The interrupt status registers record the interrupt requests in the corresponding control
bits in the interrupt control registers. The global interrupt (GIE) is enabled by the ENI
instruction and is disabled by the DISI instruction. The interrupt flag bit must be cleared
by instructions before leaving the interrupt service routine to avoid recursive interrupts.
The flags in the Interrupt Status Register are set regardless of the status of their
corresponding mask bits or the execution of DISI. Note that the logic AND of an
interrupt flag and its corresponding interrupt control bit is 1 which makes the program
counter point to the right interrupt vector. Refer to Fig. 12-1. The RETI instruction ends
the interrupt routine and enables the global interrupt (the execution of ENI).
Before the interrupt subroutine is executed, the contents of ACC, SR and ROMPS will
be saved by the hardware. After the interrupt service routine is finished, ACC, SR and
ROMPS will be pushed back.
78 •
Product Specification (V1.0) 10.09.2007
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
