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Δάσκαλος Πληροφορικής ΠΕ86

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Updated 9/2019

Lion CPU has 16 bit data and now 19 bit address bus. It has 8 registers A0 to A7. Also it has a loop index register IDX, a status register SR, a stack pointer SP, a register named OtherDataPage ODP and the program counter PC. All registers are 16-bit.
 
Execution starts at address $0020 (32) this is after the interrupt table. The stack pointer is initially set at $FFFE the end of first ram page 0.
Interrupt table is 16 words-interrupt vectors long INT 0 to 15, Interrupts 0-3 are hardware driven interrupts and INT 15 is the trap interrupt. Interrupts 4 to 14 are for software. Some interrupts are remapped by system rom to fixed address table at ram.
 
Memory paging support has been added to Lion by using 9bits of the status register.
For code execution and branching bits 15,14,13 of status register become the bits A18,A17,A16 of the address and PC or the instruction specified address (16bits) fill the rest A15..A0 address bits.
The same when data access to the memory is performed status register bits 12,11,10 become A18,A17,A16.
Finally in stack operations bits 9,8,7 of the SR become the most significant bits of the address.
So in a way similar to x86 segments, code, data and stack can be located in different pages.
 
With 3 bits 8 pages can be addressed of 64K each. There are of course special instructions to set the current page, jump to and move from or to a page. For movement of data between pages register ODP holds the source or destination page.
When Lion starts all Pages code,data,stack point to the first Page, Page 0.
On interrupt all the current page values are saved in stack by pushing the sr and the current code page is set to 0. On return from interrupt they are restored.
 
Memory map
 
Total Memory is 128K bytes (up to 512K).
$00000 - $0001F   Interrupt vector table 16 words
$00020 - $01FFF   ROM  (8K in fpga)
$02000 - $0FFFF   RAM Page 0
$10000 - $1FFFF RAM Page 1
 
Video ram is mapped at IO address space
$8000 - $FFFF   Dual port Video Ram 32K in I/O space (fpga internal)
Sprite ram 12K is mapped at IO address space
$4000 - $6FFF
 
 
HARDWARE SIGNALS of Lion system.
Line INT when low sets the interrupt,lines I1 and I0 define the interrupt vector and lines IACK, IA1,IA0 acknowledge the service of the interrupt.
Line RESET resets the CPU when LOW.
Line Clock is the clock 50MHz .
Lines A0-A18 are the address bus and D0-15 the data bus
Line RD can be used to insert wait states.
Line HOLD active low releases the buses after finishing the current instruction and CPU sets HOLDA to acknowledge.
Line AS is address strobe and DS is the data strobe (active low).
Line RW when high indicate a read cycle and when low a write.
Line IO indicates an input output operation.
Line BACS when high indicates a byte access.
Lines Rx,Tx are the serial receive and transmit signals.
Lines R,G,B,Vsync,Hsync for VGA support .
Lines MOSI,MISO,CCS,SCLK for SPI
Lines AUDIOA,AUDIOB,AUDIOC,NOISE Sound Channels
Lines KCLK,KDATA PS/2 keyboard
Lines JOYST1[0..4],JOYST2[0..4] 2 joysticks
 
 
Serial communication port parameters: 38400, 8 data, 1 stop, no parity, flow control none. 32 bytes read buffer, 32 bytes transmit buffer.
 
SR register bits:
(as with all registers, SR(0) is the rightmost less significant bit )
SR(0) = Carry flag
SR(1) = Overflow flag
SR(2) = Zero flag
SR(3) = Negative flag
SR(4) = JXA increase or decrease register
SR(5) = TRAP Interrupt 15 on/off (off=0 the default value)
SR(6) = Interrupt disable (default disabled)
SR(7..9)   Current StackPage
SR(10..12) Current Data Page
SR(13..15) Current Code Page
 
 
Operations
 
Operations must be aligned to even addresses (the assembler takes care of this).
Some operations have a .B extension, they are byte width  operations.
 
NOP does nothing, after lot of debugging it works fine.
 
MOV moves a 16bit word and has the form MOV destination, source
 
MOV Ax|(Ax)|(address) , Ax|address|(Ax)|(address)
 
Source can be a 16-bit number or a register or content of address constant or contents of address stored in a register
Destination can be a register,  or address or the address stored in register.
 
MOV.B moves the rightmost byte of source to rightmost byte of destination when it is a register or to the address specified.
 
expamles: MOV A0,$100      MOV.B (A0),A1   MOV (A1),(A0) 
          MOV A0,($FF00)   MOV (100),A2    MOV  (100),13
 
!!! MOV  ($100),($200) now supported
 
MOVI and MOVI.B is used to store a small number 0-15 to a register is smaller and faster.
ex. MOVI A0,9
 
SWAP Ax  swaps low and high bytes in a register
XCHG ax,ax exchanges values of registers
BSET Ax,(n|Ax) BCLR Ax,(n|Ax) Sets/clears the nth bit of Ax
 
16/5/2016 Added 3 more instructions MOVHL, MOVELH and MOVHH first argument always a register.
MOVEHL moves the low byte of source  to the high of destination.
MOVELH moves the high to the low. 
MOVEHH moves the high to the high.
 
1/6/2016
Added MOVR, MOVR.B relative move and GADR get address instructions.
 
MOVR  A1,(Label)
MOVR  (Label),A0
GADR  A1,Label gets the runtime calculated absolute address of Label. 
 
 
Arithmetic instructions
 
ADD  ADC  ADD.B  add without and with carry and add byte
SUB  SUB.B       subtraction
MULU, MULU.B     unsigned byte multiplication
ADDI  SUBBI      quick add/subtract a small number 0-15
 
Destination a register or an address.
INC  INC.B  DEC  DEC.B  Increase decrease value
 
 
result is stored in destination (first register)
 
examples: ADD A1,(100)  MUL.B  A0,10   SUB A3,(A2)   INC A0   DEC (COUNTER)
 
Division implemented only by software (signed INT 4 with A0=9, unsigned INT5,A0=6).
 
 
Logic instructions
 
Destination always a register, source a constant. 
AND OR NOT XOR  AND.B OR.B XOR.B NOT.B
SRL SLL SRL.B SLL.B logical shift, SLL Ax,n shifts Ax n bits  
SRA SLA  Arithmetic Shift
ROR ROL  Rotate
 
ex.   SLL  A0,3  Shifts Left Logically A0 register 3 bit positions
 
 
Test and branch instructions
 
CMP CMP.B  compare register or constant or value of address in a register or constant and set the flags
CMPI CMPI.B  Reg,0-15  compares register with small number, smaller and a bit faster than CMP.
CMPH  like CMP.B but compare the upper bytes.
 
examples CMP A4,A1  CMP A0,10  CMP A1,(100) CMP A0,(A3)  CMP (100),A2   CMPI A0,2
 
BTST Ax,(n,An)  Tests nth bit of register Ax and sets the zero flag
 
JMP JR  Jump to an absolute or relative address
 
ex. JMP (A1)  JR A0  JMP $FF7E  JR 8
 
JSR JRSR Jump to subroutine pushes next address to the stack
RET Return from subroutine restores PC from stack
 
JZ JE JNZ, JRZ, JRNZ Jump depending on zero flag (absolute and relative)
JC JNC JRC Jump depending on carry flag
JO JNO JRO Jump depending on overflow flag
JN JP  JRN Jump depending if negative or positive
 
JBE JA JAE JRBE JRA  Jump below or equal, above, above or equal for unsigned values
JLE JRLE JG JGE JRG JRLE JRG JRGE as above for signed values
 
 
Loop instructions
 
SETX Sets IDX index register to a Value,register,indirect
JMPX JRX Jump if not zero and decrease IDX 
 
example:
        SETX   3
loop:   SRL    A0,1
        JMPX   loop
 
This will loop 4 times dividing A0 by 16
 
New command 21/12/2018
JXAB JXAW JRXAB JRXAW same as JMPX JRX but if IDX is non zero increases a specified register to act as pointer to a byte or word
 
example:
      SETX 99
      MOV  A2,address1
loop: MOV.B (A2),0
      JXAB A2,loop
 
This fills 100 bytes starting at address1 with zeros.
 
 
MOVX Ax moves the value of IDX to register Ax
 
 
Stack and interrupts
 
PUSH pushes Ax or SR or (Ax) to the stack decreasing SP by 2
POP  pops AX or SR from the stack increasing SP by 2
PUSHX POPX pushes/pops IDX
SETSP Ax|address|(Ax)|(address) Sets the stack pointer to a new address
GETSP Ax Stores sp value in Ax
 
MOV SP,Ax also valid
 
ADD SP,Ax
SUB SP,Ax
 
INT n Jumps to the nth interrupt vector pushing PC and SR
RETI  Returns from interrupt restoring SR and PC
 
STI Enables interrupts
CLI Disable interrupts
 
When a hardware interrupt occurs interrupts are disabled by default until the end of service.
 
 
I/O instructions
 
IN Ax, address|Ax|(Ax) inputs a word
OUT, OUT.B address|Ax , value|Ax|(Ax) outputs a word, byte
 
Memory Paging instructions
 
Page number values are 0 to 7
 
SDP (number or An) Set data page
SSP (number or An) Set the stack page
PJMP Address,Page  Set code page and jump to address
PJSR Address,Page  Set code page and jump to subroutine at address
PRET  Return restoring code page
PMOV PMOV.B  An,(address) or (address),An move a word/byte from/to address of the Page contained in the  ODP register
SODP (n or An) Set ODP register
 
    SODP 1
    PMOV A0,(100) ; Move word from address 100 of page 1 to A0
 
 
Block move & block fill instructions
 
The IDX register that is used as a loop counter and index, is used by the transfer instructions to hold the number of words to be moved.
Instructions MTOM, MTOI, ITOM, ITOI with two arguments An1,An2 move fast blocks of words starting from memory or IO address An2 to memory or IO address An1. Instructions NTOM, NTOI with arguments An1,N or An1,An2 fill the block pointed by An1 of size IDX+1 with the 16 bit value N (or An2).
Also there are the byte by byte block move instructions MTOM.B MTOI.B ITOM.B ITOI.B 
 
MOV A1,buffer1
MOV A2,buffer2
SETX 99
MTOM A1,A2  ;copy the 100 words block starting at buffer2 to buffer1
SETX 99
NTOM A2,0   ;fill buffer2 with zeros
 
 
Assembler directives
 
PAGE number define 64K Page
ORG address position following code start at address
 
[name] DW w1,w2,...wn (auto align in even address)
[name] DB b1.b2...bn
[name] DS count in bytes
[name] TEXT "some text"
[name] DA (address constant, also auto aligned)
 

The System I/O map

Port 0, OUT Serial byte to send
Port 2, IN Serial send/receive command
Port 4, IN Serial byte received
Port 6, IN Serial status and Serial Keyboard statuus
Port 8, OUT Sound channel 1 divider/duration/start word
Port 9, IN audio channel status
Port 10, OUT Sound channel 2 divider/duration/start word
Port 11, OUT Audio noise channel enable for each audio channel bits 0-2, 1=enable 0=disable
Port 12, OUT Sound channel 3 divider/duration/start word
Port 13, OUT Enable interrupt #2 at vsync signal
Port 14, IN PS/2 Keyboard data in
Port 15, IN PS/2 Keyboard read command
Port 16, IN SPI data read
Port 17, IN SPI status
Port 18, OUT SPI data to send
Port 19, OUT SPI control
Port 20, OUT sprite buffer change
Port 20, IN read 16-bit timmer 1KHz
Port 21, IN Vsync, Hsync status bits 0,1
Port 22, IN Joystick status
Port 23, IN Current horizontal line number
Port 24, OUT Video mode
Port 25, OUT channel 1 volume 8bit
Port 26, OUT channel 2 volume 8bit
Port 27, OUT channel 3 volume 8bit
Port 28, OUT noise volume 8bit
Port 30, OUT vector display mode
Port 31-33, Second frequency for channel 1 to 3, bits 0 to 3
 
 
System Interrupts
 

;  INT4 FUNCTION TABLE  function in a0
INT4T0    DA    SERIN    ; Serial port in A1  A0(0)=1
INT4T1    DA    SEROUT   ; Serial port out A1  
INT4T2    DA    PLOT     ; at X=A1,Y=A2 A4=1 set A4=0 clear
INT4T3    DA    CLRSCR   ; CLEAR SCREEN
INT4T4    DA    PUTC     ; Print char A1 at x A2.H  y A2.L
INT4T5    DA    PSTR     ; Print zero & cr terminated string
INT4T6    DA    SCROLL   ; Scrolls screen 1 char (8 points) up
INT4T7    DA    SKEYBIN  ; PS/2 Keyboard port in A1 A0(2)=1
INT4T8    DA    MULT     ; Multiplcation A1*A2 res in A2A1, a0<>0 overflow
INT4T9    DA    DIV      ; integer Div A2 by A1 res in A1,A0
INT4T10   DA    KEYB     ; converts to ascii the codes from keyboard
INT4T11   DA    SPI_INIT ; initialize spi sd card
INT4T12   DA    SPISEND  ; spi send/rec byte in A1 mode A2 1=CS low 3=CS h res a0
INT4T13   DA    READSEC  ; read in buffer at A2, n in A1 512bytes
INT4T14   DA    WRITESEC ; WRITE BUFFER at A2 TO A1 BLOCK
INT4T15   DA    VSCROLL  ; Scroll vertically a defined window in mode 1

;  INT5 FUNCTION TABLE  function in a0
INT5T0    DA    FMULT    ; Fixed point multiply A1*A2
INT5T1    DA    FDIV     ; Fixed point divide A2.(FRAC2)/A1.(FRAC1)
INT5T2    DA    FILELD   ; Load file A4 points to filename, at A3
INT5T3    DA    VMOUNT   ; Load First Volume, return A0=fat root 1st cluster
INT5T4    DA    FILEDEL  ; Delete file A4 points to filename
INT5T5    DA    FILESAV  ; Save memory range to file A4 points to filename
INT5T6    DA    UDIV     ; Unsigned 16bit  Div A2 by A1 res in A1,A0
INT5T7    DA    LDIV     ; 32bit div A1A2/A3A4 res A1A2 rem A3A4
INT5T8    DA    LMUL     ; 32bit mult A1A2*A3A4 res A1A2
INT5T9    DA    FLMUL    ; float mult A1A2*A3A4 res A1A2
INT5T10   DA    FLDIV    ; float div A1A2/A3A4 res A1A2
INT5T11   DA    FLADD    ; float add A1A2+A3A4 res A1A2
INT5T12   DA    FCMP     ; float cmp  A1A2,A3A4 res A0 (1,0,-1)
INT5T14   DA    LINEXY   ; plot a line a1,a2 to a3,a4 (to be implemented)
INT5T15   DA    HSCROLL  ; Scroll horizontally a defined window in mode 1
INT5T16   DA    FINDF    ; A4 pointer to filename, A0 return cluster relative to (FSTCLST)