EMIF Module Architecture
823
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
External Memory Interface (EMIF)
21.2.8 Reset and Initialization Considerations
The EMIF memory controller has two active-low reset signals, CHIP_RST_n and MOD_G_RST_n. Both
these reset signals are driven by the device system reset signal. This device does not offer the flexibility to
reset just the EMIF state machine without also resetting the EMIF controller's memory-mapped registers.
As soon as the device system reset is released (driven High), the EMIF memory controller immediately
begins its initialization sequence. Command and data stored in the EMIF memory controller FIFOs are
lost. Refer the Architecture chapter of the tecnical reference manual (TRM) for more information on
conditions that can cause a device system reset to be asserted.
When system reset is released, the EMIF automatically begins running the SDRAM initialization sequence
described in
. Even though the initialization procedure is automatic, a special procedure,
found in
must still be followed.
21.2.9 Interrupt Support
The EMIF supports a single interrupt to the CPU.
details the generation and internal
masking of EMIF interrupts.
21.2.9.1 Interrupt Events
There are three conditions that may cause the EMIF to generate an interrupt to the CPU. These conditions
are:
•
A rising edge on the EMIF_nWAIT 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 EMIF_nWAIT 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 EMIF_nWAIT pin within the number of cycles defined by the MAX_EXT_WAIT bit in AWCC
(this happens only in extended wait mode). EMIF supports only linear incrementing and cache line wrap
addressing modes . If an access request for an unsupported addressing mode is received, the EMIF will
set the LT bit in the EMIF 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 EMIF 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 EMIF 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 EMIF interrupt raw register (INTRAW) and the EMIF 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.