User's Manual

Table Of Contents
STATIC MEMORY CONTROLLER S3C2450X RISC MICROPROCESSOR
5-4
3.1 ASYNCHRONOUS READ
Figure 5-3 shows an external memory read transfer with two output enable delay states, WSTOEN = 2, and two
wait states, WSTRD = 2. Four AHB wait states are inserted during the transfer, two for the standard read, and
additional two because of the programmed wait states added.
The PSMAVD signal might be required for synchronous static memory devieces when you use it in asynchronous
mode. You can disable this using the AddrValidReadEn bit in the SMBCRx register. This bit defaults to being set
(enable) to enable a system to boot from synchronous memory. You can then clear it if you do not require it.
When disabled, the signal is driven HIGH continuously.
SMCLK
ADDR
DATA(IN)
Asynchronous Read
nCS
nOE
A
D(A)
WSTRD=2
WSTOEN=2
Figure 5-3. External Memory Two Output Enable Delay State Read
SMCLK
ADDR
DATA ( R )
nCS
nWAIT
A
D(A)
nOE
Figure 5-4. Read Timing Diagram (DRnCS = 1, DRnOWE = 0)