YFNS vs YFNZ Message #1 Posted by Howard Owen on 21 Dec 2011, 9:38 p.m.
THe 41CL ROM library contains two versions of the CL extra functions ROM. They differ only in their ROM labels and in their XROM numbers. The YFNZ ROM has XROM 15, and is the default version. (i.e. it is loaded when the MMU is disabled, hardwired into port 7.) The"alternate" version is called YFNS. It has an XROM number of 31.
In order to play with flash memory on the 41CL, it is necessary to map one or the other of these ROMs into RAM. For some reason, people writing code like that tend to map the YFNS version at ROM address 0x062000 into RAM, rather than the default YFNZ version at ROM address 0x070000. They often also "restore" the port mapping of the YFNS version when they are through. This has caused me some confusion, because code I wrote using the YFNZ version fails to work if the YFNS version is loaded.
Is there an XROM collision that leads people to prefer YFNS over YFNZ? Or perhaps this is a legacy of the beta test era?
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