Fujitsu Microelectronics Europe
MCU-AN-389013-E-V10
Application Note
EE PROM Interface Routines for Xicor X25080
using the Synchronous Serial Interface (SSI)
Fujitsu Mikroelektronik GmbH
Vers. 1.0 by E. Bendels
This Application Note shows that for example a X25080 EE PROM from Xicor can be directly
connected to the SII interface of Fujitsu´s 8-bit microcontrollers and provides some usefull subroutine
functions to handle the data transfer.
Background
The SSI interface is a rather simple peripheral function found on all 8-bit Microcontrollers.
It basically consists of a simple 8-bit shift register and a control register. (See fig.1)
The controller software can byte-wise read from or write to the shift register.
When setting a start bit in the control register, the 8-bit data is shifted within 8 clock cycles.
At each clock cycle, one bit-information will appear at the output signal OUT.
At the same time, the level on the input signal IN will be shifted into the shift register at the other end.
OUT
IN
Shift Register
Clock &
Control
CLK
Microcontroller
Internal 8-bit Bus
Fig. 1, SSI Basic Block Diagram
The clock signal can be generated by the microcontroller (Master Mode), or can be provided externally
(Slave Mode). The shift direction, MSB first or LSB first can also be configured.
Parameters which can not be configured are the fixed data-length of always 8-bits, and the timing
protocol.
© Fujitsu Microelectronics Europe GmbH
-1-
MCU-AN-389013-E-V10
The basic SSI timing diagram is given in fig. 2.
On the SSI interface, once a data transfer is started, the clock signal will go from its inactive Hi-level
to Lo-level. The output signal OUT will be set according to the bit content at the falling edge.
At the following rising edge, (Lo to Hi transition) the SSI interface will sample the input signal IN.
This way, for example two microcontrollers could be directly connected and exchange data.
(Of course IN and OUT must be cross-connected and one must work in master and the other in slave
mode.)
Fujitsu SSI Basic Timing Diagram
CLK
IN
OUT
MSB
LSB
Fig. 2
When it comes to connecting other things like serial EEPROMs, this timing does not always fit.
For example to connect a SPI™ (Serial Peripheral Interface) compatible NM25C04 from National, an
external inverter would be needed to invert the clock signal output.
Of course, such problems can be worked around by implementing the serial interface only in software,
using some standard I/O lines.
This would also be the only solution if the serial protocol is even more complicated like the
MICROWIRE™ protocol from National, which is not always based on a multiple of 8-bits data
format.
Obviously a parallel to serial conversion and vice versa implemented in software is significantly
slower than utilizing a shift register.
MCU-AN-389013-E-V10
-2-
© Fujitsu Microelectronics Europe GmbH
Talking to Xicor
Fortunately some of the Xicor EEPROMs (which by the way also conform to one of the SPI modes)
fits with the Fujitsu protocol, so they can be directly connected to the SSI interface without additional
logic.
The Xicor protocol does not comply 100% with the SSI timing, as can be seen by comparing fig. 2 and
3, but technically this difference does not matter.
Xicor X25080 Basic Timing Diagram
CLK
IN
OUT
-CS
MSB
LSB
Fig. 3
The only difference is, that the clock signal for the EEPROM should be at low level at the beginning
and at the end of a transfer (the inactive time when chip select is at high level).
If directly connected to the Fujitsu SSI interface, this will not be the case since the SSI interface will
keep the clock signal at a high level during inactive time.
In practice, this difference does not matter as tests have been proven.
Important is, that data outputs on the SSI and EEPROM outputs change at the falling clock edges,
and data inputs on the SSI and EEPROM inputs take place at rising clock edges, and this is still the
case.
Typical data transfer to/from the EEPROM usually consist of quite long serial words, but fortunately
the number of bits is always a multiple of 8-bits, so the data transfer can be established by a number of
single 8-bit transfers, using the SSI interface.
For example, to read some bytes out of the EEPROM, the controller would have to do the following
steps:
1. Activate the EEPROM chip select signal by a standard output pin.
2. Send a “Read Command” byte to the EEPROM
(1st Byte Transfer (send))
3. Send the read start address to the EEPROM (HiByte)
(2nd Byte Transfer (send))
4.
“
(LoByte) (3rd Byte Transfer (send))
5. Read the 1st data byte
(4th Byte Transfer (receive))
x.
“ following bytes if required
(x
(receive))
y. Deactivate the EEPROM chip select signal again.
© Fujitsu Microelectronics Europe GmbH
-3-
MCU-AN-389013-E-V10
Benefits
Of course the main advantage of using the SSI is, that it allows faster transfers compared to a pure
software solution.
The following table gives some comparison between software and SSI supported interface functions,
based on a maximum main clock speed of 10Mhz.
The maximum serial bit rate is a more theoretical figure, since also for the SSI supported version,
some software overhead is necessary to transfer data to the serial shift register and to monitor the
control register.
The other figures present more realistic figures measured from activating the EEPROM chip select
until deactivating it again.
Maximum Serial Bit Rate
Read Status Operation
Read One Data Byte
Read 10 Data Bytes
Bytes
Transf.
2
4
14
Software Implementation
SSI supported Implementation
(Rotate, Bit Instructions, etc.) (Clock Speed = CLK/2)
9,5 Gs
0,8 Gs
180 Gs
25 Gs
370 Gs
60 Gs
1200 Gs
230 Gs
The “EE.asm” example program in appandix A, demonstrates the SSI / EEPROM interface routines on
a MB89630 Evaluation Kit.
The “EES.asm” contains some of these functions in a pure software implementation and was used to
demonstrate the difference in performance.
MCU-AN-389013-E-V10
-4-
© Fujitsu Microelectronics Europe GmbH
Appendix A
$lo cy xr cp
;+----------------------------------------------------------------------+
;¦
F U J I T S U
¦
;¦
¦
;¦
M i k r o e l e k t r o n i k
G m b H
¦
;¦
¦
;¦ Filename:
EE.asm
¦
;¦ Description:
Xicor X25080 Functions using the SSI-Interface
¦
;¦
¦
;¦ Series:
MB89630
¦
;¦ Version:
V01.00
¦
;¦ Design:
Edmund Bendels 22.10.96
¦
;¦ Change:
¦
;+----------------------------------------------------------------------+
NAME
"XICOR"
; module name
&SET DebugFunctions 0
; Flag: Do Not Include Debug Functions
&INCLUDE "c:\FJ_8L_3\INCLUDE\eBIOS.inc";
just BIOS Macros
SYCC
EQU
7
; System Speed Controll
;==
CHG3
PDR3
DDR3
SMR1
SDR1
ILR1
Some
EQU
EQU
EQU
EQU
EQU
EQU
Port Definitions
00Dh
00Dh
00Eh
01Ch
01Dh
07Ch
;===
Protocoll Equates
X_RdSr
EQU
H'05
X_WrEn
EQU
H'06
X_Read
EQU
H'03
X_Write
EQU
H'02
X_IN
X_OUT
X_CLK
X_CS
EQU
EQU
EQU
EQU
==
===
5
4
3
0
;
;
;
;
;
;
Port 3 Change Register
Port 3 Data Register
Port 3 Direction Register
Serial 1 Mode register
Serial 1 Data register
Interrupt Controler Level Register
; Cmd : Read Status
;
Write Enable
;
Read Data
;
Write Data
; SCI-Interface Bit Definitions
;----------------------------------------;-Dummy Segment Definitions
-;----------------------------------------DIRVAR DIRSEG
RB 1
DIRVAR ENDS
;----------------------------------------;----------------------------------------DVAR
DSEG
Str
RB 32
DVAR
ENDS
;*****************************************
;-Demo Program Reset Entry
-;*****************************************
Code
CSEG ABS
ORG H'2000
Reset:
Main:
;
MOV
MOVW
MOVW
MOVW
PRSTR
SYCC,#H'1F
SP,#0280H
A,#H'0030
PS,A
DemoProgMsg
;
;
;
;
;
CALL
CALL
InitSSI
StartMsg
; Init SSI-Interface
;
CALL
BenchMark
; Read 1 and 10 Bytes (Benchmark)
CALL X_WriteEnable
CALL X_ReadStatus
PrHexB SDR1
MainL:
Hi Speed MainClock
Init Stack Pointer (Internal RAM)
IL = 3 !
Init PS register
Print Initial Message
; Read Status Byte
;== Interactive Demonstration of Read / Write Strings ==
PRSTR MainLoop
RdChar
CMP
A,#'r'
BNE
CkWr
PRSTR ReadMsg
;-- REAR String from EEPROM -MOVW EP,#Str
; Target Address
MOVW A,#0
; EE-PROM Source Address
MOV
R0,#32
; max. 32 characters
CALL X_ReadData
© Fujitsu Microelectronics Europe GmbH
-5-
MCU-AN-389013-E-V10
PRSTR Str
JMP
MainL
CkWr:
Stop:
CMP
BNE
PRSTR
RDSTR
MOVW
CALL
MOV
MOVW
MOVW
CALL
JMP
A,#'w'
MainL
WriteMsg
Str,32
EP,#Str
StrLen
R0,A
A,#0
EP,#Str
X_WriteData
MainL
NOP
JMP
Stop
StrLen: PUSHW
FindEnd:MOV
BEQ
INCW
INCW
JMP
GotLen: MOVW
POPW
RET
;-- WRITE String into EEPROM -;
;
;
;
compute length of String
copy actual Str.Len into R0
EE-PROM Target Address
Controller Source Address
IX
A,@EP
GotLen
EP
IX
FindEnd
A,IX
IX
StartMsg:
PRSTR Started
RdChar
RET
;----------------------------------------;-Benchmark Tests
-;----------------------------------------BenchMark:
CALL ReadOneByte
; Performance Test 1
CALL StartMsg
;
CALL ReadTenByte
; Performance Test 2
JMP
StartMsg
;
ReadOneByte:
MOVW A,#0
; EE-PROM Source Address
MOVW EP,#Str
; Target Address
MOV
R0,#1
; max. 32 characters
JMP
X_ReadData
ReadTenByte:
MOVW A,#0
; EE-PROM Source Address
MOVW EP,#Str
; Target Address
MOV
R0,#10
; max. 32 characters
JMP
X_ReadData
MCU-AN-389013-E-V10
-6-
© Fujitsu Microelectronics Europe GmbH
;=========================================
;==
Xicor X25080 Interface Routines
==
;=========================================
;------------------------------------------------;-Initialise Port(CS) and SSI-Interface
-;------------------------------------------------InitSSI:
MOV PDR3,#H'FD
; DeActiveate CS
MOV DDR3,#H'03
; P30 = ChipSelect = Output
MOV SMR1,#B'00110010
; SCK,-SO Output, Int.Clock, MSB 1st
RET
;------------------------------------------------;-Transfer Write Enable Command
-;------------------------------------------------X_WriteEnable:
CLRB PDR3:X_CS
; Activate CS-EEPROM
MOV SDR1,#X_WrEn
; Write Enable Command
SETB SMR1:0
; Start Transfer
WaTra0: BBC SMR1:7,WaTra0
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
SETB PDR3:X_CS
; DeActivate CS-EEPROM
RET
;------------------------------------------------;-Read Status Register
-;------------------------------------------------X_ReadStatus:
CLRB PDR3:X_CS
; Activate CS-EEPROM
MOV SDR1,#X_RdSr
; Read Status Command
SETB SMR1:0
; Start Transfer
WaTra1: NOP
BBC SMR1:7,WaTra1
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
SETB SMR1:0
; Start Transfer 2nd Time
WaTra2: NOP
BBC SMR1:7,WaTra2
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
MOV A,SDR1
; read input
SETB PDR3:X_CS
; DeActivate CS-EEPROM
RET
;------------------------------------------------;-Read Bytes from EEPROM
-;-EP : Target Address
-;-A
: EEPROM Source Address
-;-R0 : Byte Count
-;------------------------------------------------X_ReadData:
CLRB PDR3:X_CS
; Activate CS-EEPROM
MOV SDR1,#X_Read
; Read Data Command
SETB SMR1:0
; Start Transfer
WaTra3: BBC SMR1:7,WaTra3
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
SWAP
MOV SDR1,A
; Transfer MS-Address Byte
SETB SMR1:0
; Start Transfer
WaTra4: BBC SMR1:7,WaTra4
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
SWAP
MOV SDR1,A
; Transfer LS-Address Byte
SETB SMR1:0
; Start Transfer
WaTra5: BBC SMR1:7,WaTra5
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
RTraLop:MOV SDR1,#0
; just dummy
SETB SMR1:0
; Start Data Transfer
WaTra6: BBC SMR1:7,WaTra6
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
MOV A,SDR1
; get received byte
MOV @EP,A
; store received byte
INCW EP
DEC R0
BNE RTraLop
; continue
SETB PDR3:X_CS
; DeActivate CS-EEPROM
RET
© Fujitsu Microelectronics Europe GmbH
-7-
MCU-AN-389013-E-V10
;------------------------------------------------;-Write Bytes to EEPROM (Max 32 Bytes)
-;-EP : Controller Souce Address
-;-A
: EEPROM Target Address
-;-R0 : Byte Count
-;------------------------------------------------X_WriteData:
CLRB PDR3:X_CS
; Activate CS-EEPROM
MOV SDR1,#X_Write
; Write Data Command
SETB SMR1:0
; Start Transfer
WaTra7: BBC SMR1:7,WaTra7
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
SWAP
MOV SDR1,A
; Transfer MS-Address Byte
SETB SMR1:0
; Start Transfer
WaTra8: BBC SMR1:7,WaTra8
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
SWAP
MOV SDR1,A
; Transfer LS-Address Byte
SETB SMR1:0
; Start Transfer
WaTra9: BBC SMR1:7,WaTra9
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
WTraLop:MOV A,@EP
; load Byte
INCW EP
MOV SDR1,A
;
SETB SMR1:0
; Start Data Transfer
WaTraA: BBC SMR1:7,WaTraA
; wait until Transfer completed
CLRB SMR1:7
; clear interrupt flag
DEC R0
BNE WTraLop
; continue
SETB PDR3:X_CS
; DeActivate CS-EEPROM
RET
;----------------------------------------;-Some Const. Data
-;----------------------------------------DemoProgMsg
DB 13,10
DB 13,10,"*****************************"
DB 13,10,"** XiCor EE-PROM Functions **"
DB 13,10,"*****************************",13,10,0
Started
DB 13,10,"PDR3-Interface Initialized"
DB 13,10,"(Start Logic Analizer for Timing Measurement)",0
MainLoop
DB 13,10
DB 13,10,"Command Loop ('R' : ReadEEStr, 'W' : WriteEEStr)",0
ReadMsg
DB 13,10,"R: ",0
WriteMsg
DB 13,10,"W:>",0
Done
DB " End ",0
;----------------------------------------;-Some Symbol Info for Monitor
-;----------------------------------------SymTab DB "SymTab:",0
; Symbol Table Header
DB LabL1-LabS1,0
; Length of 1st Symbol, dummy byte
LabS1
DB "Reset"
; Symbol Name
LabL1
DW Reset
; Symbol Value
DB LabL2-LabS2,0
LabS2
DB "Main"
LabL2
DW Main
DB LabL3-LabS3,0
LabS3
DB "Stop"
LabL3
DW Stop
DB 00
; End of Symbol Table
DB 01
; 0 BreakPoint
DW Stop
Code
ENDS
;----------------------------------------;-Symbol Table Entry
-;----------------------------------------SVector cseg ABS
ORG BIOST+24h
; Pointer to Symbol Table
DW SymTab
SVector ends
;----------------------------------------;-Reset Vector
-;----------------------------------------RVector CSEG ABS
;
ORG H'FFFC
;
DB 0
;
DB 1
;
ResVec DW Reset
;
RVector ends
;
END
MCU-AN-389013-E-V10
-8-
© Fujitsu Microelectronics Europe GmbH
Appendix B
$lo cy xr cp
;+----------------------------------------------------------------------+
;¦
F U J I T S U
¦
;¦
¦
;¦
M i k r o e l e k t r o n i k
G m b H
¦
;¦
¦
;¦ Filename:
EE.asm
¦
;¦ Topic:
Xicor X25080 EEPROM Functions
¦
;¦
(pur Software Implementation)
¦
;¦ Series:
MB89630
¦
;¦ Version:
V01.00
¦
;¦ Design:
Edmund Bendels 22.10.96
¦
;¦ Change:
¦
;+----------------------------------------------------------------------+
NAME
"XICOR"
; module name
&SET DebugFunctions 0
; Flag: Do Not Include Debug Functions
&INCLUDE "c:\FJ_8L_3\INCLUDE\eBIOS.inc";
just BIOS Macros
SYCC
EQU
7
; System Speed Controll
;==
CHG3
PDR3
DDR3
SMR1
SDR1
ILR1
Some
EQU
EQU
EQU
EQU
EQU
EQU
Port Definitions
00Dh
00Dh
00Eh
01Ch
01Dh
07Ch
;===
Protocoll Equates
X_RdSr
EQU
H'05
X_WrEn
EQU
H'06
X_Read
EQU
H'03
X_Write
EQU
H'02
X_IN
X_OUT
X_CLK
X_CS
EQU
EQU
EQU
EQU
==
===
5
4
3
0
;
;
;
;
;
;
Port 3 Change Register
Port 3 Data Register
Port 3 Direction Register
Serial 1 Mode register
Serial 1 Data register
Interrupt Controler Level Register
; Cmd : Read Status
;
Write Enable
;
Read Data
;
Write Data
; SCI-Interface Bit Definitions
;----------------------------------------;-Dummy Segment Definitions
-;----------------------------------------DIRVAR DIRSEG
RB 1
DIRVAR ENDS
;----------------------------------------;----------------------------------------DVAR
DSEG
Str
RB 32
DVAR
ENDS
;*****************************************
;-Demo Program Reset Entry
-;*****************************************
Code
CSEG ABS
ORG H'2000
Reset:
Main:
;
MOV
MOVW
MOVW
MOVW
PRSTR
SYCC,#H'1F
SP,#0280H
A,#H'0030
PS,A
DemoProgMsg
;
;
;
;
;
CALL
CALL
InitSSI
StartMsg
; Init SSI-Interface
;
CALL
BenchMark
; Read 1 and 10 Bytes (Benchmark)
CALL X_ReadStatus
MOV
R0,A
PrHexB R0
PRSTR
MOVW
MOVW
MOV
CALL
PRSTR
Stop:
NOP
JMP
StartMsg:
PrMsg
A,#0
EP,#Str
R0,#32
X_ReadData
Str
Hi Speed MainClock
Init Stack Pointer (Internal RAM)
IL = 3 !
Init PS register
Print Initial Message
; Read EE-Prom Status
; EE-PROM Source Address
; Target Address
; max. 32 characters
Stop
© Fujitsu Microelectronics Europe GmbH
-9-
MCU-AN-389013-E-V10
PRSTR Started
RdChar
RET
;----------------------------------------;-Benchmark Tests
-;----------------------------------------BenchMark:
CALL ReadOneByte
; Performance Test 1
CALL StartMsg
;
CALL ReadTenByte
; Performance Test 2
JMP
StartMsg
;
ReadOneByte:
MOVW A,#H'0000
; EE-PROM Source Address
MOVW EP,#Str
; Target Address
MOV
R0,#1
; max. 32 characters
JMP
X_ReadData
ReadTenByte:
MOVW A,#0
; EE-PROM Source Address
MOVW EP,#Str
; Target Address
MOV
R0,#10
; max. 32 characters
JMP
X_ReadData
;=========================================
;==
Xicor X25080 Interface Routines
==
;=========================================
;------------------------------------------------;-Initialise Port(CS,CLK)
-;------------------------------------------------InitSSI:
MOV PDR3,#H'F3
; DeActiveate CS, CLK=Lo
MOV DDR3,#H'1F
; P30..P34 = Output
RET
;------------------------------------------------;-- Software Parallel to Serial (Tx) Conversion -;------------------------------------------------TxByte: MOV R1,#8
TxLop: ROLC A
BC
SetBit
ClrBit: CLRB PDR3:X_OUT
BNC NxTxB
SetBit: SETB PDR3:X_OUT
NxTxB: SETB PDR3:X_CLK
; Generate Positive Edge
CLRB PDR3:X_CLK
; Generate Negative Edge
DEC R1
BNE TxLop
RET
;------------------------------------------------;-- Software Serial to Parallel (Rx) Conversion -;------------------------------------------------RxByte: MOV R1,#8
RxLop: BBS PDR3:X_IN,BitSet
BitClr: CLRC
BNC RxBil
BitSet: SETC
RxBil: ROLC A
SETB PDR3:X_CLK
; Generate Positive Edge
CLRB PDR3:X_CLK
; Generate Negative Edge
DEC R1
BNE RxLop
RET
MCU-AN-389013-E-V10
- 10 -
© Fujitsu Microelectronics Europe GmbH
;------------------------------------------------;-Read Status Register
-;------------------------------------------------X_ReadStatus:
CLRB PDR3:X_CS
; Activate CS-EEPROM
MOV A,#X_RdSr
; Read Status Command
CALL TxByte
; Tx Byte
CALL RxByte
SETB PDR3:X_CS
; DeActivate CS-EEPROM
RET
;------------------------------------------------;-Read Bytes from EEPROM
-;-EP : Target Address
-;-A
: EEPROM Source Address
-;-R0 : Byte Count
-;------------------------------------------------X_ReadData:
CLRB PDR3:X_CS
; Activate CS-EEPROM
MOV A,#X_Read
; Read Data Command
CALL TxByte
; Tx Byte
SWAP
; HiAdr into AL
CALL TxByte
; Tx Byte
XCH A,T
; restore LoAdr
CALL TxByte
; Tx Byte
RTraLop:CALL RxByte
MOV @EP,A
; store received byte
INCW EP
DEC R0
BNE RTraLop
; continue
SETB PDR3:X_CS
; DeActivate CS-EEPROM
RET
(LoAdr in TL)
;----------------------------------------;-Some Const. Data
-;----------------------------------------DemoProgMsg
DB 13,10
DB 13,10,"*****************************"
DB 13,10,"** XiCor EE-PROM Functions **"
DB 13,10,"*****************************",13,10,0
Started
DB 13,10,"PDR3-Interface Initialized"
DB 13,10,"(Start Logic Analizer for Timing Measurement)",0
PrMsg
DB 13,10,"EEPROM : ",0
;----------------------------------------;-Some Symbol Info for Monitor
-;----------------------------------------SymTab DB "SymTab:",0
; Symbol Table Header
DB LabL1-LabS1,0
; Length of 1st Symbol, dummy byte
LabS1
DB "Reset"
; Symbol Name
LabL1
DW Reset
; Symbol Value
DB LabL2-LabS2,0
LabS2
DB "Main"
LabL2
DW Main
DB LabL3-LabS3,0
LabS3
DB "Stop"
LabL3
DW Stop
DB 00
; End of Symbol Table
DB 00
; 0 BreakPoint
Code
ENDS
;----------------------------------------;-Symbol Table Entry
-;----------------------------------------SVector cseg ABS
ORG BIOST+24h
; Pointer to Symbol Table
DW SymTab
SVector ends
;----------------------------------------;-Reset Vector
-;----------------------------------------RVector CSEG ABS
;
ORG H'FFFC
;
DB 0
;
DB 1
;
ResVec DW Reset
;
RVector ends
;
END
© Fujitsu Microelectronics Europe GmbH
- 11 -
MCU-AN-389013-E-V10