Motorola MPC860 PowerQUICC, User Manual

Page: 564 / 1106

19-16 MPC860 PowerQUICC UserÕs Manual MOTOROLA
Part V. The Communications Processor Module
Table 19-11 shows the port B pin assignments for PWM mode. The respective port B pins
should be conÞgured as general-purpose outputs; see Section 34.3, ÒPort B.Ó
19.7.6 RISC Timer Initialization
Follow these steps to initialize the RISC timers:
1. Program RCCR[TIMEP] to the preferred internal timer tick interval, which
determines the scan interval for the entire timer table. The timer enable bit,
RCCR[TIME], is normally set at this time; however, it can be set later if all RISC
timers must be synchronized.
2. Determine the maximum number of timers to be located in the timer table.
ConÞgure TM_BASE to point to a location in the dual-port RAM with 4
´
N bytes
available, where N is the number of timers used. If N is less than 16, use timer 0
through timer NÐ1 to save space.
3. Clear TM_CNT to show how many ticks have elapsed since the CP internal timer
was enabled (optional).
4. Clear the RTER, if it is not already cleared. Writing 0xFFFF clears this register.
5. ConÞgure the RTMR to enable the timers that need to generate interrupts. A one
enables interrupts.
6. Set CIMR[RTT] to generate interrupts to the system. The CPIC may require
initialization not mentioned here; see Chapter 35, ÒCPM Interrupt Controller.Ó
7. ConÞgure TM_CMD. At this point, determine whether a timer is to be enabled or
disabled, one-shot or restart, and what its timeout period should be. If the timer is
being disabled, all parameters besides the timer number are ignored.
8. Issue
SET TIMER
by writing 0x0851 to the CPCR.
9. Repeat the steps 7 and 8 for each timer to be enabled or disabled.
Table 19-11. PWM Channel Pin Assignments
Timer Pairs Port B Pin
Timer 0, 1 Port B[23]
Timer 2, 3 Port B[22]
Timer 4, 5 Port B[21]
Timer 6, 7 Port B[20]
Timer 8, 9 Port B[19]
Timer 10, 11 Port B[18]
Timer 12, 13 Port B[17]
Timer 14, 15 Port B[16]