The TLCS-870 is an older microcontroller series by Toshiba. Only a few devices are still in production, and these are not recommended for new devices.
However, IMO it could still make sense to support them in SDCC since the required effort should be limited:
- The af vs wa register pair difference compared to most Z80-derivatives will require substantial work, but we need that for the TLCS-870C and TLCS-870C1 support anyway.
- The lack of ix and iy is a serious restriction, but we are already able to deal with it in the sm83 port.
- Most TLCS-870 instructions are also available in the TLCS-90 or TLCS-870C, so we get automatic support in codegen.
- However, the one TLCS-870-specific difficulty is the lack on 16-bit arithmetic on hl (the TLCS-870 has 16-bit arithmetic on wa instead). Due to this, I'd suggest to only look into a port for TLCS-870 once we have such a port for TLCS-870C or TLCS-870C1 ([feature-requests:#998]]). Maybe we can find a way to use the W register, and the 16-bit arithmetic on wa. The ports for TLCS-870C and TLCS-870C1 might profit from that, too, even though it isn't as necessary there, since those do have support for 16-bit arithmetic on hl.
