HOWTO program the Z80 SIO

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Now we do some settings for bad block counting, the first block number to expect and theRAM destination address of the file to receive from the host. See Text 13. The destinationaddress setting is red colored. From this RAM location onwards the file is to be stored. Immy example I use address 0x8000. Depending on your application you should change thisvalue.sub Ald (temp0),A ;reset bad blocks counterld C,1h ;C holds first block nr to expectld HL,8000h ;set lower destination address of filecallcallSIO_A_EIA_RTS_ONcall TX_NAK ;NAK indicates ready for transmission to hostText 13: setup 2Text 14 shows the code section that prepares the CPU for the reception of the first byte ofa data block. The line colored red makes the CPU waiting for an interrupt which is causedby the SIO. The belonging interrupt service routine is shown in Text 15.Once a block has been received, the checksum is verified and possible bad blockscounted. The same data block is transferred maximal 10 times whereupon the transfer isaborted.14
REC_BLOCK:;set block transfer modeld a,21h ;write into WR0 cmd4 and select WR1out (SIO_A_C),Ald a,10101000b ;wait active, interrupt on first RX characterout (SIO_A_C),A ;buffer overrun is a spec RX conditioneicallhaltcallA_RTS_ONA_RTS_OFF;await first rx charld a,01h ;write into WR0: select WR1out (SIO_A_C),Ald a,00101000b ;wait function inactiveout (SIO_A_C),A;check return code of block reception (e holds return code)ld a,ecp 0 ;block finished, no errorjp z,l_210cp 2 ;eot foundjp z,l_211cp 3 ;chk sum errorjp z,l_613ld a,10hjp l_612l_210: call TX_ACK ;when no errorinc c ;prepare next block to receivesub Ald (temp0),A ;clear bad block counterjp REC_BLOCKl_211: call TX_ACK ;on eotld A,01hjp l_612l_613: call TX_NAK ;on chk sum errorscfccf;clear carry flagld DE,0080h ;subtract 80hsbc HL,DE ;from HL, so HL is reset to block start addressl_612:DLD_END:ld A,(temp0) ;count bad blocks in temp0inc Ald (temp0),Acp 09hjp z,l_612 ;abort download after 9 attempts to transfer a blockjp REC_BLOCK ;repeat block receptionretText 14: Receive Data Block15
Page 3 and 4: Special attention is to be paid to
Page 5 and 6: 1.3 ProgrammingTree problems have t
Page 7 and 8: 1.3.4Initializing the CTCThe CTC ch
Page 9 and 10: 1.3.8Interrupt Service RoutinesUpon
Page 11 and 12: 2 File Transfer Mode2.1 Desired Com
Page 13: 2.2.4Initializing the CPUPlease rea
Page 17 and 18: 2.2.5.2 SubroutinesImportant for th
Page 19: 4 Useful LinksA complete embedded Z

HOWTO program the Z80 SIO

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