Memory Interfaces
4-24
4.3.2.9
EMIFS Not-Ready Functionality
The EMIFS interface includes a feature that allows an external device to assert
a not-ready signal via the OMAP5910 FLASH.RDY pin. Two modes of not-
ready are available: classic and dynamic. In either mode, if FLASH.RDY is low,
the external device is not ready.
Classic not-ready is supported for all EMIFS read modes and all access types
(read or write, single or burst). In classic not-ready mode, FLASH.RDY is
sampled synchronously at every rising TC clock edge. If FLASH.RDY is active
low, then the EMIFS interface is frozen in its current state. If there is an access
in progress, then the current state of that access is extended until the
FLASH.RDY signal goes inactive high. All information regarding the current
access is maintained (wait states, burst count, etc).
Dynamic not-ready is also supported for all accesses through EMIFS. In this
mode, FLASH.RDY is sampled synchronously to TC clock, but only after any
ongoing access (single or burst) is completed. If FLASH.RDY is sampled ac-
tive low, the EMIFS interface is placed in a hold state and remains in this state
until FLASH.RDY is asserted high by the external device. In dynamic not-
ready mode, FLASH.RDY is used by the external device to indicate to
OMAP5910 that it will be going inactive after the current access completes.
The programming of FLASH.RDY modes is described in Table 4–27, EMIF
Slow Wait State Configuration.
4.3.2.10
EMIFS Dual-Port RAM Interface Mode
The OMAP5910 EMIFS includes a programmable mode associated with the
FLASH.CS2 chip select pin to support external devices that require a valid
flash address before chip select is active. An example of such a device is a dual
port RAM (DPRAM). When DPRAM mode is enabled, the low transition of
FLASH.CS2 is delayed to ensure that address is valid. The low to high
transition of FLASH.CS2 is not changed regardless of the mode setting.
EMIFS DPRAM mode is programmed in the OMAP5910 configuration
registers using bit 22, CONF_MOD_DPRAM_ENABLE_R, in register
MOD_CONF_CTRL_0. See Chapter 6, MPU Private Peripherals, for details
on configuration registers.
DPRAM interface mode is only applicable to EMIFS chip-select FLASH.CS2.
Also note that the FLASH.CS2 pin multiplexes the FLASH.BAA function (see
Table 4–4), and this FLASH.CS2/FLASH.BAA multiplexing has highest prior-
ity. To activate the DPRAM interface mode, you must first ensure that
OMAP5910 pin multiplexing has FLASH.CS2 selected, then program for
DPRAM interface configuration as described above. The DPRAM interface