PDP-11 for the UKNC

The UKNC is a Russian home computer.

Intended for educational purposes, it's CPUs are a direct copy of the PDP-11 processor.
The UKNC actually uses Two PDP-11 processors, one for the main CPU, one for the 'Peripheral processor'... the CPU runs the main code... the PP handles Keyboard, Disk and graphics - though the main CPU can directly access 2 of the 3 graphics bitplanes (It can't access all 3

Cpu	KM181VM2 (PDP-11 Compatible) Main: 8mhz PP: 6.25mhz
Ram	Main: 64k PP: 32k
Vram	2k
Resolution	up to 640x288 @ 8 colors
Sprites
Tilemap
Colors	4 (2 bitplane) or 8 (4 bitplane) from a palette of 15
Sound chip

Emulator

UKNC BTL - Best (or only) Emulator for the UKNC

ChibiAkumas Tutorials

Useful Documentation

Ansi Escape Codes (VT100 Terminal)

Video Ports

Function	From CPU	From PPU
Select Address	177640	177010
Write Plane 0 (Blue)	(impossible)	177012
Write Plane 1 (Green)	176642	177014
Write Plane 2 (Red)	176643	177015

CPU RAM

From	To	Purpose
0	157777	RAM
160000	177777	IO

PPU RAM

From	To	Purpose
0	77777	RAM
100000	117777	RAM Window
120000	176777	ROM
177000	177777	IO

UKNC Color Palette

0	1	2	3	4	5	6	7
8	9	A	B	C	D	E	F

UKNC CPU Ports

60	CH0 IN Interrupt	Channel 0
64	CH0 OUT Interrupt	Channel 0
460	CH1 IN Interrupt	Channel 1
464	CH1 OUT Interrupt	Channel 1
474	CH2 OUT Interrupt	Channel 2
176000	Windows Register
176000	Window A register
176001	Window B register
176640	Bitplanes address register (RA)
176642	Write Plane 1 (Green) (RD)
176643	Write Plane 2 (Red) (RD)
176660	C1 in STATUS	Channel 1
176662	C1 in DATA	Channel 1
176664	C1 out STATUS	Channel 1
176666	C1 out DATA	Channel 1
176674	C2 out STATUS	Channel 2
176676	C2 out DATA	Channel 2
177560	C0 Console in STATUS	Channel 0
177562	C0 Console in DATA	Channel 0
177564	C0 Console out STATUS	Channel 0
177566	C0 Console out DATA	Channel 0

UKNC PP Ports

300	Keyboard interrupt vector
304	Programmable timer interrupt
310	External event interrupt
314	;RESET on CPU bus interrupt
320	CH0 IN Interrupt	Channel 0
324	CH0 OUT Interrupt	Channel 1
330	CH1 IN Interrupt	Channel 1
334	CH1 OUT Interrupt	Channel 2
340	CH2 IN Interrupt	Channel 2
177010	Bitplanes address register (RA)
177012	Write Plane 0 (Blue) (RD)
177014	Write Plane 1 (Green) (RD)
177015	Write Plane 2 (Red) (RD)
177016	PPU dots color
177020	PPU bitplanes 0/1 background color
177022	PPU bitplanes 1/2 background color
177024	PPU dots octet
177026	PPU bitplanes mask register
177054	Window (100000-117777)
177060	C0 in DATA	Channel 0
177062	C1 in DATA	Channel 1
177064	C1 in DATA	Channel 2
177066	C0 in STATUS	Channel 0
177066	C1 in STATUS	Channel 1
177066	C2 in STATUS	Channel 2
177070	C0 out DATA	Channel 0
177072	C1 out DATA	Channel 1
177076	C0 out STATUS	Channel 0
177076	C1 out STATUS	Channel 1
177320	Joystick "Diana", etc.
177700	Keyboard state register
177702	Keyboard data register
177710	State register	DI------ D=Data Waiting (1=Yes) I=Interrupts Enabled(1=on)
177712	Buffer register	SKKKKKKK S=State(0=pressed 1=released) K=Keycode 0-127 (0-15 when released - parital only)
177714	Current state register
177716	System control register - Bit 7 - Beeper

UKNC RAM and VRAM

The UKNC has 192K total split into 3 banks.

The top 32k is used for VRAM, The top 32k of Bank 0 makes up the 'Blue' bitplane, The top 32k of Bank 1 makes up the 'Green' bitplane, The top 32k of Bank 2 makes up the 'Red' bitplane.

The bottom 32k is used by one of the two CPU's

The 32k of banks 1+2 are combined to make up the 64k ram used by the Main CPU (the one that runs our program)... bytes from Bank 1 are at Even Addresses, Bytes from Bank 2 are at Odd addresses of the Main CPU ram.

The 32k of Bank 0 makes up the 32k Low area of the Peripheral Processor (PP) Sub CPU (the top 32k is rom).

There is no way to 'swap' these ram banks via bankswitching, however the CPU's can access the VRAM, and the Peripheral Processor 'PP' Sub CPU can access the Main CPU's ram via the 'RAP' device.

The RAP device is a third chip which has complete access to all the memory, we select an address with one port, then write data with the other two or three (depending on CPU - the SUB PP CPU can access all 3, the main CPU can access only 2)... this is how we typically write to VRAM.

It is also possible to re-configure the SLTAB line table, and move the visible RAM into an area the CPU's can directly access, however this will reduce the RAM available for other purposes.

Physical addresses and RAP ports

CPU RAP Address select port: 176640
PP RAP Address select port : 177012

	Physical Addresses
	Bank 0 Blue VRAM	Bank 1 Green VRAM	Bank 2 Red VRAM
Used for VRAM by default	177777	177777	177777
	......	......	......
	100001	100001	100001
	100000	100000	100000
Used for RAM by default	077777	077777	077777
	......	......	......
	000001	000001	000001
	000000	000000	000000
RAP MAIN CPU Port	Impossible	176642	176643
RAP PP CPU Port	177012	177014	177015

Main CPU Memory assignment

Bytes from Banks 1+2 make alternate bytes of CPU ram

Main CPU Address	RAM Even Add	RAM Odd Addr
177776/177777	077777	077777
.............	......	......
100002/100003	040001	040001
100000/100001	040000	040000
077776/077777	037777	037777
.............	......	......
000002/000003	000001	000001
000000/000001	000000	000000

Sub CPU PP Memory assignment

Low 32k uses Bank 0 RAM (both odd and even), High 32k uses ROM (both odd and even)

Sub CPU PP address	ROM (Odd and Even)	RAM (Odd and Even)
177776/177777	077776/077777
.............	.............
100002/100003	000002/000003
100000/100001	000000/000001
077776/077777		077776/077777
.............		.............
000002/000003		000002/000003
000000/000001		000000/000001

UKNC SLTAB entries

*** Thanks to aberrant_hacker for this information on the UKNC!... he's working on a port of ChibiAkumas to the UKNC... check it out here! ***

The STAB is the line definition table, it starts at address 270, each line has two words, the first is the VRAM address of that line, the second is a pointer to the next line, and a few options... more options can be configured using a 4 word SLTAB definition.

There are 3 types of record, one uses 2 words per record, the other two use 4 words... what record is next is defined by the L and S bits of the previous line.

312 (1..312) lines is SECAM half-frame
309 (1..309) SLTAB records in total (lines 4..312 of SECAM's half-frame)
scanlines 1..19 are not visible due to the vertical blanking interval
scanlines 20..307 are visible (lines 23-310 of SECAM's half-frame)
scanlines 308..309 are not visible due to the vertical blanking interval

2 word
record

V=Vram Address

C=Toggle Cursor on/off L=Length of next record (2/4 words)
S= 4-word selector (Options/Palette) / 2-word address bit 2 A=Address bits 3-15

4 word
record

Options

YRGB=Cursor color & Brightness / T=Type (Char/Graphic) / G=Graphic Cursor pos / C=Cursor pos

RGB= Line Brightness S=Scale (640/320/160/80)

V=Vram Address

C=Toggle Cursor on/off L=Length of next record (2/4 words)
S= 4-word selector (Options/Palette) / 2-word address bit 2 A=Address bits 3-15

4 word
record

palette

Palette bit combos %011 %010 %001 %001

Palette bit combos %111 %110 %101 %100

V=Vram Address

C=Toggle Cursor on/off L=Length of next record (2/4 words)
S= 4-word selector (Options/Palette) / 2-word address bit 2 A=Address bits 3-15

UKNC Keyboard Scancodes

We can read the keyboard only from the PPU, The best way is by writing our own Keyboard interrupt handler, and copying it's address to memory address #300 in octal... This will cause it to execute each time a key is pressed or released.

We can then read port 177702 to get the details of the key that was pressed.

Bit 7 will be zero if a key was pressed down... Bits 0-6 will give the full keycode of the key pressed down.

Bit 7 will be 1 if a key was released up... Bits 0-3 will give the partial keycode of the key released - this means it is not possible to 100% uniquely identify the key that was released.

Bits	7	6	5	4	3	2	1	0
KeyDown	0	K	K	K	K	K	K	K
KeyUp	1	0	0	0	K	K	K	K

Octal	Decimal	Hexadecimal	key	Details
5	5	05	,	NumPad
6	6	06	АР2	Esc
7	7	07	; / +
10	8	08	К1 / К6	F1 / F6
11	9	09	К2 / К7	F2 / F7
12	10	0A	КЗ / К8	F3 / F8
13	11	0B	4 / �
14	12	0C	К4 / К9	F4 / F9
15	13	0D	К5 / К10	F5 / F10
16	14	0E	7 / '
17	15	0F	8 / (
25	21	15	-	NumPad
26	22	16	ТАБ	Tab
27	23	17	Й / J
30	24	18	1 / !
31	25	19	2 / "
32	26	1A	3 / #
33	27	1B	Е / E
34	28	1C	5 / %
35	29	1D	6 / &
36	30	1E	Ш / [
37	31	1F	Щ / ]
46	38	26	УПР	Ctrl
47	39	27	Ф / F
50	40	28	Ц / C
51	41	29	У / U
52	42	2A	К / K
53	43	2B	П / P
54	44	2C	H / N
55	45	2D	Г / G
56	46	2E	Л / L
57	47	2F	Д / D
66	54	36	ГРАФ	Graph
67	55	37	Я / Q
70	56	38	Ы / Y
71	57	39	В / W
72	58	3A	А / A
73	59	3B	И / I
74	60	3C	Р / R
75	61	3D	О / O
76	62	3E	Б / B
77	63	3F	Ю / @
105	69	45	HP	Shift
106	70	46	АЛФ	CapsLock
107	71	47	ФИКС	Lock
110	72	48	Ч / ^
111	73	49	С / S
112	74	4A	М / M
113	75	4B	SPACE	Space
114	76	4C	Т / T
115	77	4D	Ь / X
116	78	4E	←	Left
117	79	4F	, / <
125	85	55	7	NumPad
126	86	56	0	NumPad
127	87	57	1	NumPad
130	88	58	4	NumPad
131	89	59	+	NumPad
132	90	5A	ЗБ	Backspace
133	91	5B	→	Right
134	92	5C	↓	Down
135	93	5D	. / >
136	94	5E	Э / \
137	95	5F	Ж / V
145	101	65	8	NumPad
146	102	66	.	NumPad
147	103	67	2	NumPad
150	104	68	5	NumPad
151	105	69	ИСП	Execute
152	106	6A	УСТ	Settings
153	107	6B	ВВОД	Enter
154	108	6C	↑	Up
155	109	6D	: / *
156	110	6E	Х / H
157	111	6F	З / Z
165	117	75	9	NumPad
166	118	76	ВВОД	NumPad
167	119	77	3	NumPad
170	120	78	6	NumPad
171	121	79	СБРОС	Reset
172	122	7A	ПОМ	Help
173	123	7B	/ / ?
174	124	7C	Ъ / }
175	125	7D	- / =
176	126	7E	О / }
177	127	7F	9 / )