The DISCiPLE RAM layout
The DISCiPLE RAM not only holds the system file but contains also a number of 'system
variables' used for various housekeeping tasks.
Address Length Name Contents
#0000 6656 SYSTEM Holds the system file.
#1A00 195 BITMAP Here the complete disk bitmap is stored.
#1AC3 2 SECT_USED The number of sectors used by the CATalogue entry
currently being printed; start of the Disk File
Channel Area (DFCA), except the first 13 bytes it's an
exact copy of a "D" write channel.
#1AC5 2 BYTESLEFT Number of bytes left to be loaded or saved.
#1AC7 1 SCAN_TYPE Holds the scan-type during a CATalogue scan.
#1AC8 2 FILEADDR Address of first byte to be loaded or saved.
#1ACA 2 BUFLEN Length of a disk data buffer.
#1ACC 2 IFF Contents of the F register with IFF held in the P/V
#1ACE 1 CUR_DRIVE Drive number of current drive.
#1ACF 1 FLAGS3 Various flags to signal various states: (meaning
with bit set)
0 - there has at least one file been handled.
1 - serving the network or CLEAR # executing.
2 - stealing from or forcing to a PUPIL.
3 - using network.
4 - LOAD command executing.
5 - SAVE command executing.
6 - MERGE command executing.
7 - VERIFY command executing.
#1AD0 2 RPT Offset of next byte to be read from buffer. The
following 774 bytes (up to and including #1DD5) are
exactly the same as byte 13 (CHRPT) and onwards in a
#1AD2 2 BUFF Offset of buffer from start of channel = 39.
#1AD4 1 CUR_SECT Sector number of sector where this buffer will be
#1AD5 1 CUR_TRACK Track number of sector where this buffer will be
#1AD6 1 DIRDESC Directory description. Please note that the next 256
bytes are the same as a CATalogue entry.
#1AD7 10 NAME Filename.
#1AE1 2 CNT Sectors used, MSB first!
#1AE3 1 FRST_TRK First track.
#1AE4 1 FRST_SECT First sector.
#1AE5 195 BITMAP File bitmap.
#1BA8 1 LENGTH_HI File length MSB (number of 64K blocks).
#1BA9 1 TYPE File type.
#1BAA 2 LENGTH MID and LOW bytes of file length.
#1BAC 2 ADDR File address.
#1BAE 2 LENGTH_2 Length excluding variables if a BASIC file.
#1BB0 2 AUTOSTART Autostart line or address.
#1BB2 22 Z80REGS Contains IY, IX, DE', BC', HL', IF, DE, BC, HL, IF
and SP respectively (only with SNAPSHOT files).
#1BC8 14 Not used.
#1BD6 510 BUFFER Data bytes.
#1DD4 1 NXT_TRACK Next track number.
#1DD5 1 NXT_SECT Next sector number.
#1DD6 2 D_CH_ADD Address of the next character to be interpreted; the
DISCiPLE uses this address while checking a statement.
#1DD8 2 TOTAL_USED Number of used sectors on disk being CATalogued.
#1DDA 1 IN_31 Current control port state; because port 31 as control
port is write only (IN 31 reads Kempston joystick) the
contents send to it are stored here.
#1DDB 1 RETRIES Retry counter; it counts the number of retries being
made before giving an error.
#1DDC 6 ID_FIELD Whenever the FDC reports an error the ID Field of
the first encountered sector on the current track is
read and stored here; the track number is then
stored into the track register of the FDC.
#1DE2 2 Not used ?
#1DE4 1 SYST_TYPE System configuration; #44: system loaded, #4E: Pupil
station, #53: minimal system, #00: resetted once.
#1DE5 1 CALBASSING Holds #47 when executing a CALBAS.
#1DE6 2 Not used ?
#1DE8 2 LBYT_ADDR Address used while verifying from disk or while loading
or verifying from network.
#1DEA 1 A_REG Used as a temporary store for the A register.
#1DEB 2 RPT' Alternative disk buffer offset; used with SAVE TO.
RPT'-lo holds the column counter while CATalogueing
#1DED 2 SECTOR' Alternative track and sector number; used with SAVE
TO, also used as temporary store for stream data.
#1DEF 1 MAPUSED Number of files which use the bitmap at #1A00, this is
#1DF0 4 Not used ?
#1DF4 1 NTRESP Store for network response code.
#1DF5 1 NTDEST Destination station number 0-64; start of the 8 byte
#1DF6 1 NTSRCE Source station number.
#1DF7 2 NTNUMB Network block number.
#1DF9 1 NTTYPE Network packet type; 0 = normal, 1 = EOF.
#1DFA 1 NTLEN Data block length.
#1DFB 1 NTDCS Data block checksum.
#1DFC 1 NTHCS Header block checksum.
#1DFD 1 SRV_DEST Destination station number during network service;
start of the 28 byte command block (so including next
#1DFE 1 SRV_SRCE Source station number during service.
#1DFF 1 COMMAND BASIC-command code.
#1E00 1 SRV_PRT Byte to be printed by the master station during a
PRINT command. Also used during COPY SCREEN$ to hold
the type (ASCII value).
#1E01 24 UFIA1 First User File Information Area (UFIA) in DISCiPLE
#1E19 1 PAGE_CONF Page configuration during 128K snapshot.
#1E1A 24 UFIA2 Second UFIA.
#1E32 2 D_CURCHL Store for CURCHL during network servicing; start of
11 byte file descriptor during SAVE TO.
#1E34 2 D_FLAGS Store for FLAGS during network servicing.
#1E36 7 Remainder of file descriptor storage.
#1E3D 275 N_CHANNEL Whenever the network is used, this holds genuine
network channel data; when booting the system, this
holds the 13 byte 'LOAD_SYS' load system file
routine (see #220C).
#1FFD X IN_STACK Internal stack grows down from here.
#1FFE 2 D_OLD_SP Old SP when DISCiPLE internal stack in use.