AN00015.TXT

Advanced Communication Board Developer's Toolkit 1995


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Subject: Migrating from a Z8530 to a Z85C30 or Z85230.


For ACB applications that require higher data rates, the NMOS Z8530 SCC
may be upgraded to a Z85C30 SCC or Z85230 ESCC. Both the Z85C30 and Z85230
have larger FIFOs and enhanced SDLC/HDLC capabilities. The Z85230 has an
additional write register that will need to be programmed. Existing source
code or examples on this diskette can be modified easily to get the system 
up and running with a Z85C30 or Z85230. This application note covers the 
simple code modification needed. For details on fully exploiting the 
enhanced versions of the SCC, please refer to the Zilog SCC User Manual.

A new write register is added to the Z85230 ESCC. This register is called
Write Register 7 Prime or WR7'. To access this register, set bit D0 in Write
Register 15. When this bit is set, an access to Write Register 7, will 
actually access Write Register 7 Prime. In the initialization array,
program WR7' to 0 or 10 hex. Additional bits may need to be set depending the
application. Once WR7' has been programmed, reset bit D0 in Write Register
15 and program WR7 as normal.