
Architecture
870
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
External Memory Interface A (EMIFA)
The EMIFA and its registers are reset when any of the following events occur:
1. The RESET pin on the device is asserted
2. An emulator reset is initiated through the Code Composer Studio™ integrated development
environment
In the first case, the EMIFA will exit the reset state when RESET is released and after the PLL controller
releases the entire device from reset. In the second case, the EMIFA will exit the reset state immediately
after the emulator reset is complete.
In both cases, the EMIFA automatically begins running the SDRAM initialization sequence described in
after coming out of reset. Even though the initialization procedure is automatic, a special
procedure, found in
must still be followed.
19.2.8 Interrupt Support
The EMIFA supports a single interrupt to the CPU.
details the generation and internal
masking of EMIFA interrupts, and
describes how the EMIFA interrupts are sent to the
CPU.
19.2.8.1 Interrupt Events
There are three conditions that may cause the EMIFA to generate an interrupt to the CPU. These
conditions are:
•
A rising edge on the EMA_WAIT signal (wait rise interrupt)
•
An asynchronous time out
•
Usage of unsupported addressing mode (line trap interrupt)
The wait rise interrupt occurs when a rising edge is detected on EMA_WAIT signal. This interrupt
generation is not affected by the WP
n
bit in the asynchronous wait cycle configuration register (AWCC).
The asynchronous time out interrupt condition occurs when the attached asynchronous device fails to
deassert the EMA_WAIT pin within the number of cycles defined by the MAX_EXT_WAIT bit in AWCC
(this happens only in extended wait mode). EMIFA supports only linear incrementing and cache line wrap
addressing modes . If an access request for an unsupported addressing mode is received, the EMIFA will
set the LT bit in the EMIFA interrupt raw register (INTRAW) and treat the request as a linear incrementing
request.
Only when the interrupt is enabled by setting the appropriate bit
(WR_MASK_SET/AT_MASK_SET/LT_MASK_SET) in the EMIFA interrupt mask set register
(INTMSKSET) to 1, will the interrupt be sent to the CPU. Once enabled, the interrupt may be disabled by
writing a 1 to the corresponding bit in the EMIFA interrupt mask clear register (INTMSKCLR). The bit fields
in both the INTMSKSET and INTMSKCLR may be used to indicate whether the interrupt is enabled. When
the interrupt is enabled, the corresponding bit field in both the INTMSKSET and INTMSKCLR will have a
value of 1; when the interrupt is disabled, the corresponding bit field will have a value of 0.
The EMIFA interrupt raw register (INTRAW) and the EMIFA interrupt mask register (INTMSK) indicate the
status of each interrupt. The appropriate bit (WR/AT/LT) in INTRAW is set when the interrupt condition
occurs, whether or not the interrupt has been enabled. However, the appropriate bit
(WR_MASKED/AT_MASKED/LT_MASKED) in INTMSK is set only when the interrupt condition occurs
and the interrupt is enabled. Writing a 1 to the bit in INTRAW clears the INTRAW bit as well as the
corresponding bit in INTMSK.
contains a brief summary of the interrupt status and control bit
fields. See
for complete details on the register fields.