SBSRAM Interface
9-45
External Memory Interface
Table 9–17. EMIF SBSRAM Pins
EMIF Signal
SBSRAM Signal
SBSRAM Function
SSADS
ADSC
Address strobe
SSOE
OE
Output enable
SSWE
WE
Write enable
SSCLK/CLKOUT2/ECLKOUT
CLK
SBSRAM clock
SBSRAMs are latent by their architecture, meaning that read data follows
address and control information. Consequently, the EMIF inserts cycles between
read and write commands to ensure that no conflict exists on the ED[31:0] bus.
The EMIF keeps this turnaround penalty to a minimum. The initial 2-cycle penalty
occurs when the direction changes on the bus. In general, the first access of a
burst sequence incurs a 2-cycle start-up penalty.
9.5.1
SBSRAM Reads
Figure 9–32 shows a four-word read of an SBSRAM for the ’C6201/C6202/
C6701. Every access strobes a new address into the SBSRAM, indicated by
the SSADS strobe low. The first access requires an initial start-up penalty of
two cycles; thereafter, all accesses occur in a single SSCLK cycle.
Figure 9–32. SBSRAM Four-Word Read
BE1
BE2
BE3
BE4
A1
A2
A3
A4
Q1
Q2
Q3
Q4
Clock†
CEx
BE[3:0]
EA[21:2]
ED[31:0]
SSADS
SSOE
SSWE
Read
Read
Read
D1
latched
Read
D2
latched
D3
latched
D4
latched
† Clock=SSCLK for ’C6201/C6701.
Clock=CLKOUT2 for ’C6202.