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i.MX27 Data Sheet, Advance Information, Rev. 0.1
28
Preliminary—Subject to Change Without Notice
Freescale Semiconductor
Signal Descriptions
Table 3
shows the i.MX27 signal descriptions.
Table 3. i.MX27 Signal Descriptions
Pad Name
Function/Notes
External Bus/Chip Select (EMI)
A [13:0]
Address bus signals, shared with SDRAM/MDDR, WEIM and PCMCIA, A[10] for
SDRAM/MDDR is not the address but the pre-charge bank select signal.
MA10
Address bus signals for SDRAM/MDDR
A [25:14]
Address bus signals, shared with WEIM and PCMCIA
SDBA[1:0]
SDRAM/MDDR bank address signals
SD[31:0]
Data bus signals for SDRAM, MDDR
SDQS[3:0]
MDDR data sample strobe signals
DQM0–DQM3
SDRAM data mask strobe signals
EB0
Active low external enable byte signal that controls D [15:8], shared with PCMCIA PC_REG.
EB1
Active low external enable byte signal that controls D [7:0], shared with PCMCIA PC_IORD.
OE
Memory Output Enable—Active low output enables external data bus, shared with PCMCIA
PC_IOWR.
CS [5:0]
Chip Select—The chip select signals CS [3:2] are multiplexed with CSD [1:0] and are selected
by the Function Multiplexing Control Register (FMCR) in the System Control chapter. By default
CSD [1:0] is selected. DTACK is multiplexed with CS4.
CS[5:4] are multiplexed with ETMTRACECLK and ETMTRACESYNC; PF22, 21.
ECB
Active low input signal sent by flash device to the EIM whenever the flash device must terminate
an on-going burst sequence and initiate a new (long first access) burst sequence.
LBA
Active low signal sent by flash device causing external burst device to latch the starting burst
address.
BCLK
Clock signal sent to external synchronous memories (such as burst flash) during burst mode.
RW
RW signal—Indicates whether external access is a read (high) or write (low) cycle. This signal
is also shared with the PCMCIA PC_WE.
RAS
SDRAM/MDDR Row Address Select signal
CAS
SDRAM/MDDR Column Address Select signal
SDWE
SDRAM Write Enable signal
SDCKE0
SDRAM Clock Enable 0
SDCKE1
SDRAM Clock Enable 1
SDCLK
SDRAM Clock
SDCLK_B
SDRAM Clock_B
NFWE_B
NFC Write enable signal, multiplexed with ETMPIPESTAT2; PF6
NFRE_B
NFC Read enable signal, multiplexed with ETMPIPESTAT1; PF5
NFALE
NFC Address latch signal, multiplexed with ETMPIPESTAT0; PF4