Register Descriptions
1232
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
External Peripheral Interface (EPI)
17.11.5 EPI Host-Bus 8 Configuration (EPIHB8CFG) Register, offset 0x010
NOTE:
The MODE field in the EPICFG register determines which configuration register is accessed
for offsets 0x010 and 0x014.
To access EPIHB8CFG, the MODE field must be 0x2.
The Host Bus 8 Configuration register is activated when the HB8 mode is selected. The HB8 mode
supports muxed address/data (overlay of lower 8 address and all 8 data pins), separate address/data, and
address-less FIFO mode. Note that this register is reset when the MODE field in the EPICFG register is
changed. If another mode is selected and the HB8 mode is selected again, the values must be
reinitialized.
This mode is intended to support SRAMs, Flash memory(read), FIFOs, CPLDs/FPGAs, and devices with
an MCU/Host Bus slave or 8-bit FIFO interface support.
If less address pins are required, the corresponding AFSEL bit (see the
GPIO
chapter) should not be
enabled so the EPI controller does not drive those pins, and they are available as standard GPIOs.
EPI Host-Bus 8 Mode can be configured to use one to four chip selects with and without the use of ALE. If
an alternative to chip selects are required, a chip enable can be handled in one of three ways:
1. Manually control via GPIOs.
2. Associate one or more upper address pins to CE. Because CE is normally CE, lower addresses are
not used. For example, if pins EPI0S27 and EPI0S26 are used for device 1 and 0 respectively, then
address 0x6800.0000 accesses device 0 (device 1 has its CE high), and 0x6400.0000 accesses
device 1 (device 0 has its CE high). The pull-up behavior on the corresponding GPIOs must be
properly configured to ensure that the pins are disabled when the interface is not in use.
3. With certain SRAMs, the ALE can be used as CEn because the address remains stable after the ALE
strobe. The subsequent WR or RD signals write or read when ALE is low thus providing CE
functionality.
Figure 17-32. EPI Host-Bus 8 Configuration (EPIHB8CFG) Register [offset 0x010]
31
30
29
28
27
26
24
CLKGATE
CLKGATEI
CLKINV
RDYEN
IRDYINV
Reserved
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R-0
23
22
21
20
19
18
16
XFFEN
XFEEN
WRHIGH
RDHIGH
ALEHIGH
Reserved
R/W-0
R/W-0
R/W-0
R/W-0
R/W-1
R-0
15
8
MAXWAIT
R/W-1
7
6
5
4
3
2
1
0
WRWS
RDWS
Reserved
MODE
R/W-0
R/W-0
R-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 17-18. EPI Host-Bus 8 Configuration (EPIHB8CFG) Register Field Descriptions
Bit
Field
Value
Description
31
CLKGATE
Clock Gated
0
The EPI clock is free running.
1
The EPI clock is held low.