
Functional Overview
176
December 2003 Revised March 2005
SPRS231D
3.8
Shared Peripherals
The shared peripherals are connected to both the MPU Public Peripheral bus and the DSP Public Peripheral
bus. Connections are achieved via a TI Peripheral Bus Switch, which must be configured to allow MPU or DSP
access. The other shared peripherals have permanent connections to both public peripheral buses, although
read and write accesses to each peripheral register may differ.
3.8.1 Mailbox Registers
Four sets of shared mailbox registers are available for communication between the DSP and MPU:
Two reads/writes accessible by the MPU, read-only by the DSP
Two reads/writes accessible by the DSP, read-only by the MPU
Each mailbox is implemented with 2
×
16-bit registers. When a processor writes to a register, it generates an
interrupt; this interrupt is released by a read access by the other processor.
These registers are discussed further in Section 3.12,
Interprocessor Communication.
3.8.2 General-Purpose Timers
OMAP5912 consists of eight 32-bit timers with the following features:
Counter timer with compare and capture modes
Autoreload mode
Start-stop mode
Programmable divider clock source
16-/32-bit addressing
On-the-fly read/write registers
Interrupts generated on overflow, compare, and capture
Interrupt enable
Wake-up enable
Write posted mode
Dedicated input trigger for capture mode and dedicated output trigger/PWM signal
Each timer module contains a free-running upward counter with autoreload capability on overflow. The timer
counter can be read and written on-the-fly (while counting). The timer module includes compare logic to allow
interrupt event on programmable counter matching value. A dedicated output signal can be pulsed or toggled
on overflow and match event. This offers timing stamp trigger signal or PWM (pulse width modulation) signal
sources. A dedicated input signal can be used to trigger automatic timer counter capture and interrupt event,
on programmable input signal transition type. A programmable clock divider (prescaler) allows reduction of
the timer input clock frequency. All internal timer interrupt sources are merged into one module interrupt line
and one wake-up line. Each internal interrupt sources can be independently enabled/disabled with a dedicated
bit of the TIER register for the interrupt features and a dedicated bit of TWER for the wake-up.