The TI 5TI-1029 looks to be a prom based memory unit, so you can't program it directly. You might want to open it up and check the memory board.
The 5TI-1034 series was the latest made with read/write memory. IIRC, the CPU of all 5TI's is about 9" x 12", brushed alumn. finish.
To the best of my knoledge, you had to send the program to TI to get proms made. I never did.
The 5TI r/w memory units could be programmed by the hand held unit or the VPU terminal unit - both I used many times. If you didn't have a VPU you used a cassette tape unit for backup/restore and a datalink unit to a serial printer for listing the ladder to paper.
The 505 series is a totally different beast. I don't recall if the VPU could program it.