W40S01-04 Datasheet, PDF (5/10 Pages) Cypress Semiconductor – SDRAM Buffer - 4 DIMM

W40S01-04
How To Use the Serial Data Interface
Electrical Requirements
Figure 1 illustrates electrical characteristics for the serial inter-
face bus used with the W40S01-04. Devices send data over
the bus with an open drain logic output that can (a) pull the bus
line LOW, or (b) let the bus default to logic 1. The pull-up resis-
tor on the bus (both clock and data lines) establish a default
logic 1. All bus devices generally have logic inputs to receive
data.
Although the W40S01-04 is a receive-only device (no data
write-back capability), it does transmit an “acknowledge” data
pulse after each byte is received. Thus, the SDATA line can
both transmit and receive data.
The pull-up resistor should be sized to meet the rise and fall
times specified in AC parameters, taking into consideration to-
tal bus line capacitance.
9''
9''
6(5,$/ %86 '$7$ /,1(
6(5,$/ %86 &/2&. /,1(
&/2&. ,1
&/2&. 287
6'&/.
'$7$ ,1
1 '$7$ 287
a NΩ
a NΩ
6'$7$
1
&/2&. ,1
6&/2&.
'$7$ ,1
'$7$ 287
6'$7$
1
&+,3 6(7
6(5,$/ %86 0$67(5 75$160,77(5
&/2&. '(9,&(
6(5,$/ %86 6/$9( 5(&(,9(5
Figure 1. Serial Interface Bus Electrical Characteristics
5