The SP ROM by Comprocsys Ltd was an add-on card for the ZX81 that provided 256 x 192 bitmapped graphics, reading and writing of EPROMs and communication with peripherals through a Zilog 8255 PIA chip. It could be used in conjunction with the Comprocsys ASZMIC ROM or without (via ZX81 BASIC commands).
I have created a disassembly of the SP ROM from a scanned printout of a disassembly I created from the ZX81 to an Epson Dot Matrix printer in 1985.
It is available as a .zip file here which contains the binary sp-rom.rom file as well as the .asm source file and an Xcode project file.
(.zip file updated 2016-08-17)
The original manual has been scanned and is available as a .PDF file here.
Original scanned printouts from 1985 disassembly are available as a series of searchable .PDF files here.
zasm assembler can be found here.
See article Assembling Z80 Assembler .zasm source files with BBEdit and Zasm Z80 Assembler below for more information.