Problem connecting to telnet via modem using Z80 assembly language

[apdavis]

I have been trying to connect to a TCP socket on a computer on my network running the telnet service using Z80 assembly language and the CP/M Assembler v2.0. When I execute the assembled code using the ddt debugger with the command 'g100' I do not receive a TCP connection from the IMSAI8080esp. Can anyone explain why? Thanks

    ORG 100H       

    ; Send initialization command
    LD HL, Init
    CALL OUTPUT_STRING

    ; Send connection command
    LD HL, Connect
    CALL OUTPUT_STRING
    RET

Init:
    DB 'ATZ', 13, 0         ; Reset modem 

Connect:
    DB 'ATD192.168.33.34:23', 13, 0	; connect to telnet service on 192.168.33.34

OUTPUT_STRING:
    LD A, (HL)
    OR A
    RET Z
    OUT (36), A            ; SIO2.B 36 (data), 37 (status)
    INC HL
    JR OUTPUT_STRING

[ronaldlw]

I'm still learning, but it looks like you have assembly errors in your code:

I>asm apdavis
CP/M ASSEMBLER - VER 2.0

L                   LD HL, Init
E0100 CD0000        CALL OUTPUT_STRING
L                   LD HL, Connect
E0103 CD0000        CALL OUTPUT_STRING
P               OUTPUT_STRING:
S                   LD A, (HL)
S                   OR A
S0121 C9            RET Z
S0122 D324          OUT (36), A            ; SIO2.B 36 (data), 37 (status)
L                   INC HL
0124
000H USE FACTOR
END OF ASSEMBLY

I'll try to mess with it later tonight if you don't figure it out first!

[ronaldlw]

k, my curiosity got the best of me and I poked on it a bit.

I think you must be reading the wrong manual, what assembly language are you using?

You should be using the 8080 manual that is in the MAN: icon on the IMSAI web ui.

I am not sure what exactly you're trying to do so I might have things wrong, but this code at least compiles (what is the JR supposed to do?):

I>type apdavis.prn


 0100           ORG 100H       
                
                    ; Send initialization command
                ;    LD HL, Init
 0100 210D01        LXI H,Init
E0103 CD0000        CALL OUTPUT_STRING
                
                    ; Send connection command
                    ;LD HL, Connect
 0106 210D01        LXI H,Init
E0109 CD0000        CALL OUTPUT_STRING
 010C C9            RET
                
                Init:
 010D 41545A0D00    DB 'ATZ', 13, 0         ; Reset modem 
                
                Connect:
 0112 4154443139    DB 'ATD192.168.33.34:23', 13, 0     ; connect to telnet service on 192.168.33.34
                
S               OUTPUT_STRING:
                    ;LD A, (HL)
 0127 7D            MOV A,L
                    ;OR A
 0128 B7            ORA A
                    ;RET Z
 0129 C8            RZ
                    ;OUT (36), A            ; SIO2.B 36 (data), 37 (status)
 012A D324          OUT 36
                    ;INC HL
 012C 23            INX H 
E012D C30000        JMP OUTPUT_STRING
 0130               END

A good way to see if a compile is successful (the asm output is pretty cryptic and I don't really understand it yet either) is to look at the output PRN file. If you see lines of your code that doesn't have corresponding opcodes to the left
of it then the assembler wasn't able to understand it.

I've found this reference card very handy:
8080-8085_Reference_Card_HEX.pdf

[ronaldlw]

the call is obviously wrong, not sure what's up with that. hopefully this will get you going in the right direction at least. Using the debugger is helpful too

You can get to the first instruction by typing g100,100 that will take you to address 100 and then break. From there you can do l to list and t to trace (run one instruction and break. etc.. there's a lot of good info in the cpm manual under the ddt section on that.

[apdavis]

Thanks for your help - you were right - I should have been using 8080 assembly language instead of Z80. This code now works to establish a TCP connection:

        ORG     100H        ; Program origin at address 0100H

INIT:   DB      'ATZ', 13, 0        ; Define the string 'ATZ', followed by a carriage return and null terminator
CONN:   DB      'ATD192.168.33.34:23', 13, 0 ; Define the connection string

        LXI     H, INIT             ; Load HL with the address of INIT
        CALL    OUTP                ; Call the OUTP subroutine

        LXI     H, CONN             ; Load HL with the address of CONN
        CALL    OUTP                ; Call the OUTP subroutine
        RET                         ; Return from the main routine

; OUTP subroutine: outputs the string at HL to the I/O port
OUTP:   MOV     A, M                ; Load the byte at the memory location pointed to by HL into A
        ORA     A                   ; Logical OR A with itself to check if it's 0 (end of string)
        RZ                          ; Return if zero (end of string)
        OUT     24H                 ; Output the byte in A to port 36
        INX     H                   ; Increment HL to point to the next byte
        JMP     OUTP                ; Jump back to process the next byte