*FX/OSbyte features not documented in the BBC Micro User Guide
Contents
1. 8th July 1992 Support Group Application Note a Number 020 Cor ww Issue 1 Author FEX OSbyte features not documented in the BBC Micro User Guide Applicable Related Hardware Application BBCB Notes BBC B Copyright Acorn Computers Limited 1992 Every effort has been made to ensure that the information in this leaflet is true and correct at the time of printing However the products described in this leaflet are subject to continuous Support Group development and improvements and Acorn Computers Limited reserves the right to change oc fis its specifications at any time Acorn Computers Limited cannot accept liability for any loss Acom Computer s Limited or damage arising from the use of any information or particulars in this leaflet ACORN Acorn House ECONET and ARCHIMEDES are trademarks of Acorn Computers Limited ae Vision Park Histon Cambridge CB44AE Support Group Application Note No 020 Issue 1 8th July 1992 amp 0D 13 Two undocumented parameters may be supplied in X to disable events isable RS423 receive error event X 7d X 8 disable service network error event amp 0E 14 As above two undocumented parameters may be supplied in X to enable events X 7 enable RS423 receive error event X 8 enable service network error event Events are explained on p465 of the User Guide amp 76 117 This call returns the VDU status byte which contains various status flags in t2. at no character has been removed from the buffer amp 99 153 The call inserts a character into an INPUT buffer handling the interrupt character and generating an escape condition if necessary Valid only for X 0 or 1 Y must contain character to be inserted amp 9C 156 Change 6850 control register The 6859 register is altered to Old value AND Y EOR X See User Guide page 438 Refer to the 6850 Data Sheet for details of the 6850 control register amp 9E 158 amp 9F 159 These calls respectively read and write to the Speech Processor chip Refer to the Speech System User Guide amp E9 233 As for amp E7 see User Guide page 441 but affects the system 6522 The system 6522 is used extensively in the normal operation of the machine and consequently this call should be used with extreme care amp EB 235 Return presence of Speech Processor X amp FF if Speech Processor present X amp 00 if Speech Processor not present amp F1 241 Read Write FX1 value amp F5 245 Read Write FX5 value Support Group Application Note No 020 Issue 3 Support Group Application Note No 020 Issue 1 8th July 1992 amp F6 246 Read Write FX6 value THESE THREE CALLS OPERATE AS DESCRIBED IN THE USER GUIDE ON PAGE 438 amp FC 252 Reads ID of current language a number from 0 to 15 which indicates which socket the presently selected language ROM is in The sockets are numbered from right to left
3. he X register BIT 0 set if VDU2 sent cleared by VDU3 BIT 2 set if PAGED MODE ON cleared if PAGED MODE OFF BIT 3 set if software scrolling cleared if hardware scrolling Software scrolling is used when text windows have been defined whereas hardware scrolls are used when the whole screen scrolls BIT 5 set when cursors joined by VDU5S BIT 7 set if VDU disabled amp 76 118 Returns with the carry bit if the CTRL key is pressed and with the Negative bit set if the SHIFT key is pressed Machine code routines may branch on these conditions This feature is invalid when called from a Second Processor amp 7B 123 This call is used by the User Print Routine to indicate to the MOS that it has finished its task CF FX 5 3 command This feature should not normally be called from a Second Processor amp 8A 138 This call has been expanded to allow a character to be inserted into any buffer X must contain the buffer number and Y the character to be inserted A list of buffer numbers appears with FX 21 on p428 of the User Guide amp 8D 141 This command is exactly equivalent to the ROM command Support Group Application Note No 020 Issue 2 Support Group Application Note No 020 Issue 1 8th July 1992 amp 98 152 This call examines a buffer The buffer number must be in X and the call returns as follows Carry bit set if buffer empty Carry bit clear indicates character s present in buffer Note th
4. starting at 15 On board sockets are 15 14 13 12 and the remainder can be installed offboard This call may not be meaningful from a Second Processor since there may not necessarily be a current language in this case amp FD 253 Returns a number indicating what sort of reset last occurred 0 Soft Break 1 Power on Break 2 CTRL Break amp FE 254 Read Write available RAM in BBC microcomputer even when called from Second Processor 128 32K 64 16K amp FF 255 Read Write start up option byte This allows the keyboard link value to be read it may be written to but the value will be reset to the actual wired value on any reset other than a soft reset The links are configured as follows L 2 3 4 5 6 7 8 X X D _ D B M M M 2 1 3 2 1 D2 D1 Disc configuration bits see Disc Manual B Auto boot select Auto boot when fitted M3 M2 M1 Screen mode on hard reset 0 7 X Unused Support Group Application Note No 020 Issue 4
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