register, the
CSCFG
field and the
CSCFGEXT
bit in the
EPIHBnCFGn
register, and the
BSEL
bit in
the
EPIHB16CFG
register. The
CSCFGEXT
bit extends the chip select configuration possibilities by
providing the most significant bit of the
CSCFG
field. Refer to Table 11-4 on page 827 for the possible
ALE and chip select options that can be programmed by the combination of the
CSCFGEXT
and
CSCFG
bits. Note that
CSCFGEXT
is the most significant bit.
Table 11-4. CS CSCFG Encodings
Description
Value
ALE Configuration
EPI0S30
is used as an address latch (ALE). The ALE signal is generally used when the address and data
are muxed (
MODE
field in the
EPIHB8CFG
register is 0x0). The ALE signal is used by an external latch to
hold the address through the bus cycle.
0x0
CSn Configuration
EPI0S30
is used as a Chip Select (CSn). When using this mode, the address and data are generally not
muxed (
MODE
field in the
EPIHB8CFG
register is 0x1). However, if address and data muxing is needed,
the
WR
signal (
EPI0S29
) and the
RD
signal (
EPI0S28
) can be used to latch the address when CSn is low.
0x1
Dual CSn Configuration
EPI0S30
is used as CS0n and
EPI0S27
is used as CS1n. Whether CS0n or CS1n is asserted is determined
by the most significant address bit for a respective external address map. This configuration can be used
for a RAM bank split between 2 devices as well as when using both an external RAM and an external
peripheral.
0x2
ALE with Dual CSn Configuration
EPI0S30
is used as address latch (ALE),
EPI0S27
is used as CS1n, and
EPI0S26
is used as CS0n.
Whether CS0n or CS1n is asserted is determined by the most significant address bit for a respective external
address map.
0x3
ALE with Single CSn Configuration
EPI0S30
is used as address latch (ALE) and
EPI0S27
is used as CSn.
0x4
Quad CSn Configuration
EPI0S30
is used as CS0n and
EPI0S27
is used as CS1n. EPI0S34 is used as CS2n and EPI0S33 is used
as CS3n.
0x5
ALE with Quad CSn Configuration
EPI0S30
is ALE,
EPI0S26
is CS0n and
EPI0S27
is used as CS1n. EPI0S34 is used as CS2n and EPI0S33
is used as CS3n.
0x6
Reserved
0x7
If one of the Dual-Chip-Select modes is selected (
CSCFGEXT
is 0x0 and
CSCFG
is 0x2 or 0x3 in the
EPIHBnCFGn
register), both chip selects can share the peripheral, code, or the memory space, or
one chip select can use the peripheral space and the other can use the memory or code space. In
the
EPIADDRMAP
register, if the
EPADR
field is not 0x0, the
ECADR
field is 0x0, and the
ERADR
field is 0x0, then the address specified by
EPADR
is used for both chip selects, with CS0n being
asserted when the MSB of the address range is 0 and CS1n being asserted when the MSB of the
address range is 1. If the
ERADR
field is not 0x0, the
ECADR
field is 0x0, and the
EPADR
field is 0x0,
then the address specified by
ERADR
is used for both chip selects, with the MSB performing the
same delineation. If both the
EPADR
and the
ERADR
are not 0x0, and the
ECADR
field is 0x0 and the
EPI is configured for dual-chip selects, then CS0n is asserted for either address range defined by
EPADR
and CS1n is asserted for either address range defined by
ERADR
. The two chip selects can
also be shared between the code space and memory or peripheral space. If the
ECADR
field is 0x1,
ERADR
field is 0x0, and the
EPADR
field is not 0x0, then CS0n is asserted for the address range
defined by
ECADR
and CS1n is asserted for either address range defined by
EPADR
. If the
ECADR
field is 0x1,
EPADR
field is 0x0, and the
ERADR
field is not 0x0, then CS0n is asserted for the address
range defined by
ECADR
and CS1n is asserted for either address range defined by
ERADR
.
827
June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C1294NCPDT Microcontroller