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Data
Data
Data
Data
FFULL
(EPIOS27)
Frame
(EPIOS30)
FEMPTY
(EPIOS26)
WRn
(EPIOS29)
RDn
(EPIOS28)
Data
Data
Data
FFULL
(EPIOS27)
Frame
(EPIOS30)
FEMPTY
(EPIOS26)
WRn
(EPIOS29)
RDn
(EPIOS28)
Initialization and Configuration
1115
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
External Peripheral Interface (EPI)
Figure 16-17. Write Followed by Read to External FIFO
Figure 16-18. Two-Entry FIFO
16.4.4 General-Purpose Mode
The General-Purpose Mode Configuration (EPIGPCFG) register is used to configure the control, data, and
address pins, if used. Any unused EPI controller signals can be used as GPIOs or another alternate
function. The general-purpose configuration can be used for custom interfaces with FPGAs, CPLDs, and
digital data acquisition and actuator control.
General-Purpose mode is designed for three general types of use:
•
Extremely high-speed clocked interfaces to FPGAs and CPLDs. Three sizes of data and optional
address are supported. Framing and clock-enable functions permit more optimized interfaces.
•
General parallel GPIO. From 1 to 32 pins may be written or read, with the speed precisely controlled
by the EPIBAUD register baud rate (when used with the WFIFO and/or the NBRFIFO) or by the rate of
accesses from software or µDMA. Examples of this type of use include:
–
Reading 20 sensors at fixed time periods by configuring 20 pins to be inputs, configuring the
COUNT0 field in the EPIBAUD register to some divider, and then using nonblocking reads.
–
Implementing a very wide ganged PWM/PCM with fixed frequency for driving actuators or LEDs.
•
General custom interfaces of any speed.
The configuration allows for choice of an output clock (free-running or gated), a framing signal (with frame
size), a ready input (to stretch transactions), an address (of varying sizes), and data (of varying sizes).
Additionally, provisions are made for separating data and address phases.
The interface has the following optional features:
•
Use of the EPI clock output is controlled by the CLKPIN bit in the EPIGPCFG register. Unclocked uses
include general-purpose I/O and asynchronous interfaces (optionally using RD and WR strobes).