There is a good explanation of ASCII available at this site - http://daffy.robelle.com/smugbook/ascii.html
This is a sample SSH_CMSG_REQUEST_PTY Packet (Packet Type 10) taken from a Linux SSH client.

31 9d 65 fc dc 0a 00 00 00 05 76 74 31 30 32 00 00 00 36 00 00 00 51 00 00 00 21 00 00 00 00 c1 00 00 25 80 c0 00 00 25 80 01 03 02 1c 03 7f 04 15 05 04 06 00 07 00 08 11 09 13 0a 1a 0c 12 0d 17 0e 16 12 0f 1e 00 1f 00 20 00 21 00 22 00 23 00 24 01 25 00 26 01 27 00 28 00 29 00 32 01 33 01 34 00 35 01 36 01 37 01 38 00 39 00 3a 00 3b 01 3c 01 3d 01 3e 00 46 01 47 00 48 01 49 00 4a 00 4b 00 5a 01 5b 01 5c 00 5d 00 00 fe 06 d1 6a

PTY Encoded Data in red.

All this stuff took me a while to figure out and I only understood it after I put the client into debug mode and looked at the raw packets being sent.  Hopefully the breakdown here will help you with your own ssh implementations.

The Breakdown

First two opcodes have 4 byte arguments
c1 00 00 25 80 - 129 TTY_OP_ISPEED - Specifies Input Baud Rate
c0 00 00 25 80 - 128 TTY_OP_OSPEED - Specifies Output Baud Rate

Rest of the Opcodes (01 - 5D) have one byte arguments
HEXOP    HEXARG     [DECIMAL OPCODE]    Description

01 03 [01 VINTR   ] - Interrupt Character (CTRL-C)
02 1C [02 VQUIT   ] - SIGQUIT Character (CTRL-\)
03 7F [03 VERASE  ] - Erase character to left of cursor (DELETE Key)
04 16 [04 VKILL   ] - Kill the current line input (CTRL-V)
05 04 [05 VEOF    ] - End of File Character (CTRL-D)
06 00 [06 VEOL    ] - End of Line Character
07 00 [07 VEOL2   ] - Additional End of line char
08 11 [08 VSTART  ] - Continues Paused output
09 13 [09 VSTOP   ] - XON/XOFF to pause listings (CTRL-S)
0A 1A [10 VDSUSP  ] - Suspends current program (CTRL-Z)
0C 12 [12 VREPRINT] - Reprint current line (CTRL-R)
0D 17 [13 VWERASE ] - Erases a word to left of character (CTRL-W)
0E 16 [14 VLNEXT  ] - Enter next char typed literally (CTRL-V)
12 0F [18 VDISCARD] - Flushing of output terminal (CTRL-O)

The following settings are set to 00 (FALSE) or 01 (TRUE) for
their arguments.

1E 00 [30 IGNPAR  ] - Ignore Parity (FALSE)
1F 00 [31 PARMRK  ] - Mark parity and framing errors (FALSE)
20 00 [32 INPCK   ] - Enable checking of parity errors (FALSE)
21 00 [33 ISTRIP  ] - Strip Eighth Bit (FALSE)
22 00 [34 INLCR   ] - Map NL into CR on input (FALSE)
23 00 [35 IGNCR   ] - Ignore CR on input (FALSE)
24 01 [36 ICRNL   ] - Map CR to NL on input (TRUE)
25 00 [37 IUCLC   ] - Tranlsate upper to lower case (FALSE)
26 01 [38 IXON    ] - Enable output flow control (TRUE)
27 00 [39 IXANY   ] - Any char will restart after stop (FALSE)
28 00 [40 IXOFF   ] - Enable input flow control (FALSE)
29 00 [41 IMAXBEL ] - Ring bel on input queue full (FALSE)
32 01 [50 ISIG    ] - Enable INTR, QUIT, SUSP (TRUE)
33 01 [51 ICANON  ] - Canonicalize input lines (TRUE)
34 00 [52 XCASE   ] - Enable input and output of upper case with \ (FALSE)
35 01 [53 ECHO    ] - Enable echoing (TRUE)
36 01 [54 ECHOE   ] - Visually Erase chars (TRUE)
37 01 [55 ECHOK   ] - Kill character discards current line (TRUE)
38 00 [56 ECHONL  ] - Echo New Line even if ECHO is off (FALSE)
39 00 [57 NOFLSH  ] - Don't flush after interrupt (FALSE)
3A 00 [58 TOSTOP  ] - Stop background jobs from output (FALSE)
3B 01 [59 IEXTEN  ] - Enable extensions (TRUE)
3C 01 [60 ECHOCTL ] - Echo control characters as ^char (TRUE)
3D 01 [61 ECHOKE  ] - Visual erase for line kill (TRUE)
3E 01 [62 PENDIN  ] - Retype pending input (TRUE)
46 01 [70 OPOST   ] - Enable output processing (TRUE)
47 00 [71 OLCUC   ] - Conver lower case to uppercase (FALSE)
48 01 [72 ONLCR   ] - Map NL to NL-CR (TRUE)
49 00 [73 OCRNL   ] - Translate carriage return to newline (output) (FALSE)
4A 00 [74 ONOCR   ] - Translate newline to carriage return - newline
(output). (FALSE)
4B 00 [75 ONLRET  ] - Newline performs a carriage return (output) (FALSE)
5A 01 [90 CS7     ] - 7 BIT mode (TRUE)
5B 01 [91 CS8     ] - 8 BIT mode (TRUE)
5C 00 [92 PARENB  ] - Parity Enable
5D 00 [93 PARODD  ] - Odd parity, else even
00    - TTY_OP_END (End of encoding)