SX48DB: Port Write Error

Cranehill

Hello there!

I am now developing some product using two SX48ProtoBoards(with SX-Keys) which communicate with each other through RE port.
But the value I try to write in RE port connected to the other SX48·is· written differently in the register sometimes ,not always in SX-Key's Debug-Run mode.
In other words, different value is written.

The source code is as follows:

---

;////////////////////////////
; Transmit byte data
;////////////////////////////


:transmit_next_byte

··mov·W,#$1F···;Mode=Directopn
··mov·M,W
··;mov·· ·RE,#%0000_0000········ ·;must specify port before dir set
··mov···· !RE,#RW_bus_ta_TX_DIR·;transmit mode dir.

; tx upper nibble
··mov·RW_temp,RW_read_val
··and·RW_temp,#%1111_0000
··clc
··rr·RW_temp···;rotate right * 4
··rr·RW_temp
··rr·RW_temp
··rr·RW_temp
··mov·RW_tx_upper_nibble_log,RW_temp

··mov·W,RE
··and·W,#%1111_0000··;mask the lower nibble

··or·W,RW_temp
··mov·RE,W···;transmit upper nibble

··nop····;REV097Gz1e

··mov·RW_tx_upper_nibble_phy,RE

;
··nop····;read-modify-write consideration?
··nop
··nop
;
··setb·RW_STRB_to_mx_pin·;RW_STRB:the Target

---

> Master

---

For example, though W value before 'mov RE,W' is $0A, RE value after the execution of the instruction is $08.


I·don't know this problem is related with· "Read-Modify-Write Considerations" in the data sheet.
But·can you explain more details about it?

Cranehill
JAPAN
·

Bean

Cranehill,
In the code you are modifing the lower nibble. So if the RW_read_val high nibble is different then what is currently on the low nibble or RE then it will change.

So if RW_read_val = $8x (x=don't care) then RE would change from $0A to $08 after the MOV RE,W instruction.

Watch what W is doing between the MOV W,RE and the MOV RE,W that should tell you if it is working correctly.

Read-Modify-Write problem usually occur when you have two consecutive instructions that use the same port, I don't see any in your code. You have a NOP between the MOV RE,W and MOV RW_tx_upper_nibble_phy so that is good.

P.S. You can just use SWAP instead of the CLC and four rotates.

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.iElectronicDesigns.com

·

Cranehill

Thank you ! Bean,

I give you more detail.

RW_tx_upper_nibble_log·=·reg_B0
RW_tx_lower_nibble_log·=·reg_B1
RW_rx_upper_nibble_log·=·reg_B2
RW_rx_lower_nibble_log·=·reg_B3
RW_tx_upper_nibble_phy·=·reg_B4
RW_tx_lower_nibble_phy·=·reg_B5
RW_rx_upper_nibble_phy·=·reg_B6
RW_rx_lower_nibble_phy·=·reg_B7

RW_arg_cnt··=·reg_B8
RW_arg_ptr··=·reg_B9
RW_arg1···=·reg_BA
RW_arg2···=·reg_BB
RW_arg3···=·reg_BC
RW_read_val··=·reg_BD
RW_temp···=·reg_BE
RW_session_cnt··=·reg_BF

The value of RW_read_val is $AB.

Please see the attached file which includes a snap shot of SX-Key Debugger.



Cranehill



[font=ï¼*ï¼³ ゴシック]·[/font]

Bean

I don't really see anything that jumps out at me.
If you could post the complete program I could maybe see something that would help.

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.iElectronicDesigns.com

·

Cranehill

Thank you again, Bean,

All·source codes are attached.
I really appreciate your help!

Crane hill

Bean

Whoa...Way to much code to try to figure out what is going on.

Try to make the simplest shortest program that demonstrates the problem.

I see you are running at 50MHz, and Read-Modify-Write problems do occur at this speed. I would examine any code that uses the same port that is not seperated by at least a couple instructions.

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.iElectronicDesigns.com

·

Cranehill

I am sorry for the huge source codes.

I extracted the code areas that might be causing the problem.

Please see·the·extraced source codes attached.

Cranehill