Epson S1C33L03 User Manual

II CORE BLOCK: BCU (Bus Control Unit)

S1C33L03 FUNCTION PART

EPSON

B-II-4-19

A-1

B-II

BCU

Bus Cycles in External System Interface

The following shows a sample SRAM connection the basic bus cycles.

A[9:1]

D[15:0]

#RD

#WRH

#WRL

#CE

S1C33

(1) A0 system (little endian/big endian)

A[8:0]
I/O[15:0]

#RD
#WRH
#WRL
#CE

SRAM

A[9:1]

D[15:0]

#WRH

#WRL

#CE

#RD

S1C33

(2) #BSL system (little endian)

A[8:0]
I/O[15:0]

#LB
#UB
#WE
#OS
#OE

SRAM

A[9:1]

D[15:0]

#WRH

#WRL

#CE

#RD

S1C33

(3) #BSL system (big endian)

A[8:0]
I/O[15:0]

#LB
#UB
#WE
#OS
#OE

SRAM

Figure 4.18 Sample DRAM Connection

SRAM Read Cycles

Basic read cycle with no wait mode

BCLK

A[23:0]

#CExx

D[15:0]

#RD

#WAIT

;;;

;;

addr

data

Figure 4.19 Basic Read Cycle with No Wait

Read cycle with wait mode

Example: When the BCU has no internal wait mode and 2 wait cycles via #WAIT pin are inserted

;;;;;;

;;;;;

BCLK

A[23:0]

#CExx

D[15:0]

#RD

#WAIT

;;;

;;;;;;;;;;;;;;

addr

data

Figure 4.20 Read Cycle with Wait

The #WAIT signal is sampled at the falling edge of the transition of BCLK (bus clock) and when it is

sampled on an inactive (high level), the read cycle is terminated.

Note: Insertion of wait cycles via the #WAIT pin is possible only when the device for bus conditions is set

for SRAM, and SWAITE (D0) / Bus control register (0x4812E) is enabled for waiting.