Changes
8255
,/* PPI Control */
== PPI Control ==
This register has two different functions depending on bit7 of the data written to this register.If Bit 7 is "1" then the other bits will initialize Port A-B as Input or Output: Bit 0 IO-Cl Direction for Port C, lower bits (always 0=Output in CPC) Bit 1 IO-B Direction for Port B (always 1=Input in CPC) Bit 2 MS0 Mode for Port B and Port Cl (always zero in CPC) Bit 3 IO-Ch Direction for Port C, upper bits (always 0=Output in CPC) Bit 4 IO-A Direction for Port A (0=Output, 1=Input) Bit 5,6 MS0,MS1 Mode for Port A and Port Ch (always zero in CPC) Bit 7 SF Must be "1" to setup the above bits * CAUTION: Writing to PIO Control Register (with Bit7 set), automatically resets PIO Ports A,B,C to 00h each!* In the CPC only Bit 4 is of interest, all other bits are always having the same value.In order to write to the PSG sound registers, a value of 82h must be written to this register.In order to read from the keyboard (through PSG register 0Eh), a value of 92h must be written to this register. Otherwise, if Bit 7 is "0" then the register is used to set or clear a single bit in Port C: Bit 0 B New value for the specified bit (0=Clear, 1=Set) Bit 1-3 N0,N1,N2 Specifies the number of a bit (0-7) in Port C Bit 4-6 - Not Used Bit 7 SF Must be "0" in this case
== Programming Examples ==
