Page 20

Epson Research and Development

 

Vancouver Design Center

 

 

4.6 Test Software

The test software used to exercise this interface is very simple. It carries out the following functions:

1.Configures chip select 4 on the MPC821 to map the S1D13504 to an unused 4M byte block of address space.

2.Loads the appropriate values into the option register for CS4.

3.Enables the S1D13504 host bus interface by writing the value 0 to REG[1Bh].

At that point the software runs in a tight loop which reads the S1D13504 Revision Code Register REG[00h]. This allows monitoring of the bus timing on a logic analyzer.

This source code for the following test routine was entered into the memory of the MPC821ADS using the line-by-line assembler in MPC8BUG (the debugger provided with the ADS board). It was run on the ADS and a logic analyzer was used to verify operation of the interface hardware.

4.6.1 Source Code

BR4

equ

$120

; CS4 base register

OR4

equ

$124

; CS4 option register

MemStart

equ

$40

; upper word of S1D13504 start address

DisableReg

equ

$1b

; address of S1D13504 Disable Register

RevCodeReg

equ

0

; address of Revision Code Register

Start

mfspr

r1,IMMR

; get base address of internal registers

 

andis.

r1,r1,$ffff

; clear lower 16 bits to 0

 

andis.

r2,r0,0

; clear r2

 

oris

r2,r2,MemStart

; write base address

 

ori

r2,r2,$0801

; port size 16 bits; select GPCM; enable

 

stw

r2,BR4(r1)

; write value to base register

 

andis.

r2,r0,0

; clear r2

 

oris

r2,r2,$ffc0

; address mask – use upper 10 bits

 

ori

r2,r2,$0708

; normal CS negation; delay CS ½ clock;

 

 

 

; inhibit burst

 

stw

r2,OR4(r1)

; write to option register

 

andis.

r1,r0,0

; clear r1

 

oris

r1,r1,MemStart

; point r1 to start of S1D13504 mem space

 

stb

r1,DisableReg(r1)

; write 0 to disable register

Loop

lbz

r0,RevCodeReg(r1)

; read revision code into r1

 

b

Loop

; branch forever

end

 

 

 

S1D13504

Interfacing to the Motorola MPC821 Microprocessor

X19A-G-010-05

Issue Date: 01/02/02

Page 458
Image 458
Epson S1D13504 manual Test Software, Source Code