HOWTO program the Z80 SIO

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1.3.6Hardware Flow ControlIn order to signal the host whether the client is ready or not to receive a character the RTSline coming out of the client (and driving towards the host) needs to be switched. As earliersaid I assume the host is much faster than the client, that why I do not implement a routineto check the CTSline coming from the host.A_RTS_OFF:ld a,005h ;write into WR0: select WR5out (SIO_A_C),Ald a,0E8h ;DTR active, TX 8bit, BREAK off, TX on, RTS inactiveout (SIO_A_C),AretA_RTS_ON:ld a,005h ;write into WR0: select WR5out (SIO_A_C),Ald a,0EAh ;DTR active, TX 8bit, BREAK off, TX on, RTS activeout (SIO_A_C),AretText 6: signaling the host go or nogo for reception1.3.7 Disabling SIO RXchannelWhen certain conditions arise it might by important to disable the receive channel of theSIO (see routine in Text 7).SIO_A_DI:;disable SIO channel A RXld a,003h ;write into WR0: select WR3out (SIO_A_C),Ald a,0C0h ;RX 8bit, auto enable off, RX offout (SIO_A_C),A;Channel A RX inactiveretText 7: Disabling the SIO8
1.3.8Interrupt Service RoutinesUpon reception of a character the routine RX_CHA_AVAILABLE shown in Text 8 isexecuted. Here you get the character set by the host. In the end of this routine, thecharacter is sent back to the host by a simple single commandout (SIO_A_D),ANote: In this example we backup only register AF. Depending on your application youmight be required to backup more registers like HL, DE, CD, ...Routine SPEC_RX_CONDITION is executed upon a special receive condition like bufferoverrun. In my example the CPU is to jump at the warmstart location 0x0000.RX_CHA_AVAILABLE:push AF ;backup AFcall A_RTS_OFFin A,(SIO_A_D) ;read RX character into A; A holds received character;do something with the received character;echo character to hostout (SIO_A_D),Acall TX_EMPei;see comments belowcall A_RTS_ON ;see comments belowpop AF ;restore AFRetiSPEC_RX_CONDITON:jp 0000hText 8: character received routineNote: The code written in red might be required if you want the CPU to be ready foranother interrupt (ei) and to give the host a go for another transmission (call A_RTS_ON).I recommend to put these two lines not here but in your main program routine thatprocesses the characters received by the SIO. This way you process one character afteranother and avoid overrunning your SIO RX buffer.9
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Page 5 and 6: 1.3 ProgrammingTree problems have t
Page 7: 1.3.4Initializing the CTCThe CTC ch
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Page 15 and 16: REC_BLOCK:;set block transfer model
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HOWTO program the Z80 SIO

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