External Signal Connections; Refresh Configuration; Epi Sdram Signal Connections - Texas Instruments Concerto F28M35 Series Technical Reference Manual

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17.6.1 External Signal Connections

defines how EPI module signals should be connected to SDRAMs. The table applies when

using a x16 SDRAM up to 512 megabits. Any unused EPI controller signals can be used as GPIOs or

another alternate function.

EPI0S20-EPI0S27

If 2 signals are listed, connect the EPI signal to both pins.

Only for 256/512 megabit SDRAMs.

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:

/ 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 µsand is derived by dividing 1000 by the clock speed expressed

in MHz. So, 50 MHz is 1000/50=20 ns, or 0.02 µs. A typical SDRAM is 4096 rows per bank if the system

clock is running at 50 MHz with an EPIBAUD register value of 0:

RFSH = (64000/4096) / 0.02 = 15.625 µs /0.02 µs = 781.25

External Peripheral Interface (EPI)

Table 17-1. EPI SDRAM Signal Connections

SDRAM Signal

SPRUH22I – April 2012 – Revised November 2019

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