See “External Peripheral Interface (EPI)” on page 1853 for timing details for the SDRAM mode.
11.4.2.1
External Signal Connections
Table 11-3 on page 823 defines how EPI module signals should be connected to SDRAMs. The
table applies when using a x16 SDRAM up to 512 megabits. Note that the EPI signals must use
8-mA drive when interfacing to SDRAM, see page 774. Any unused EPI controller signals can be
used as GPIOs or another alternate function.
Table 11-3. EPI SDRAM x16 Signal Connections
SDRAM Signal
a
EPI Signal
D0
A0
EPI0S0
D1
A1
EPI0S1
D2
A2
EPI0S2
D3
A3
EPI0S3
D4
A4
EPI0S4
D5
A5
EPI0S5
D6
A6
EPI0S6
D7
A7
EPI0S7
D8
A8
EPI0S8
D9
A9
EPI0S9
D10
A10
EPI0S10
D11
A11
EPI0S11
D12
A12
b
EPI0S12
D13
BA0
EPI0S13
D14
BA1
EPI0S14
D15
EPI0S15
DQML
EPI0S16
DQMH
EPI0S17
CASn
EPI0S18
RASn
EPI0S19
not used
EPI0S20-EPI0S27
WEn
EPI0S28
CSn
EPI0S29
CKE
EPI0S30
CLK
EPI0S31
a. If two signals are listed, connect the EPI signal to both pins.
b. Only for 256/512 megabit SDRAMs.
11.4.2.2
Refresh Configuration
The refresh count is based on the external clock speed and the number of rows per bank as well
as the refresh period. The
RFSH
field represents how many external clock cycles remain before an
AUTO-REFRESH is required. The normal formula is:
RFSH
= (t
Refresh_us
/ number_rows) / ext_clock_period
A refresh period is normally 64 ms, or 64000 μs. The number of rows is normally 4096 or 8192. The
ext_clock_period is a value expressed in μsec and is derived by dividing 1000 by the clock speed
823
June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C1294NCPDT Microcontroller