Notes: DEC DL11

The DL11 is the basic serial line interface for the Unibus PDP-11. When addressed at 777560 it is the console. The typical Unibus implementation is the M7800 quad height SPC module. The module supports several DL11 versions, -A through -E. The differences were in the cables and the crystal supplied. The module can supply asynchronous serial signals in 3 different types: TTL, EIA (now generally called RS-232), and 20mA. The cable determines the signal type used. Four different crystals were available resulting in four Speed Groups. For modern usage, Groups 3 and 4 are the most useful.

The console cable I have is a BC05-C from cursory examination.

KL11

There is also a KL11 that was used as the console. It was 20mA only and consisted of 3 modules: M780, M105, and M7821. I have a hacked version of this, probably to adapt it for RS-232.

The M780 should be in rows C and D, the M105 in row E, and the M7821 in row F.

I have since rebuilt the KL11 to original and used it with an ASR33 as the console. The bit rate generators are analog clocks controlled by pots. The output clock can be adjusted by putting the processor in a loop outputing characters. The input clock can be adjusted by disconnecting the input cable. This sets the input to a start bit and the receiver will clock continuously.

M105 Jumpers

The console terminal is at 17 777 560. The M105 provides jumpers for bits 12 thru 3. The 18 bit console address in binary is 111 111 111 101 110 000. So the jumpers on the board should be OOO OJO OOJ.

KL11 as a PC11

The KL11 (and DL11) have the same basic CSR layout as the PC11. For the purposes of the bootstrap, they are the same. I have moved my KL11 to 17 777 550 and use it as PR in the bootstrap.

Console

The console DL11 was configured for 8-N-1. This was OK until I started using some diagnostics that set bit 7. This was not compatible with the decserver I was using for my serial interface. I changed the DL11 settings to 7-E-1.

Name	Jumper	State	Description
No Parity	NP	IN	Enable parity bit transmission and reception by installing a jumper.
Even Parity	EPS	OUT	Remove jumper for even parity.
STOP Bit	2SB	OUT	Used with J9, J10, J11. 9 out, 10 in, 11 out, 2SB out -> 2 stop bits.
Data Bits	NB1	IN	7 data bits.
Data Bits	NB2	OUT	7 data bits.

Speed Group	1	2	3	4
Crystal Freq. (Hz)	844.8k	1.03296M	1.152M	4.608M
S1, S2 POS. (T, R)	Baud Rate
1	36.7	44.8	50	200
2	55	67.3	75	300
3	110	134.5	150	600
4	220	269	300	1200
5	440	538	600	2400
6	880	1076	1200	4800
7	1320	1614	1800	7200
8	1760	2152	2400	9600

Berg	Pin	Description	Direction	Type	Active/ Passive	Description
A	40	Ground			passive
B	39	Ground			passive
C	38	Force Busy	Out	EIA	configurable	Active or passive based on jumper settings. J2, J4
D	37				n/c
E	36	Serial Input	In	TTL	active	TTL serial in, must be looped in berg, H or M.
F	35	Serial Output	Out	EIA	active	RS-232 output.
H	34	20mA Interlock	Out	TTL	active	Clamped version of K. Loop to E for 20mA.
J	33	Serial Input	In	EIA	active	RS-232 input.
K	32	Serial Input +	In	20mA	active	Diode clamps to +5 and 0.
L	31				n/c
M	30	EIA Interlock	Out	TTL	active	TTL version of J. Loop to E for RS-232.
N	29				n/c
P	28				n/c
R	27				n/c
S	26	Serial Input -		20mA	passive	Pulldown to -15.
T	25	Clear to Send	In	EIA	active
U	24				n/c
V	23	Request to Send	Out	EIA	configurable	Active or passive based on jumper settings. J1, J4
W	22				n/c
X	21	Ring	In	EIA	active
Y	20				n/c
Z	19				n/c
AA	18	Serial Output +	Out	20mA	active	Serial data source.
BB	17	Carrier	In	EIA	active
CC	16	Clock Input	In	TTL	active	Selected by HH.
DD	15	Data Terminal Ready	Out	EIA	active
EE	14	Reader Run -	Out	20mA	passive	Reader relay sink, 68ohms to -15.
FF	13	Secondary Xmit	Out	EIA	active	Uncommitted control signal.
HH	12	Clock Enable	In	TTL	active	Low selects external clock from CC
JJ	11	Secondary Receive	In	EIA	active	Uncommitted control signal.
KK	10	Serial Output -	Out	20mA	passive	Serial data sink to -15.
LL	9				n/c
MM	8				n/c
NN	7				n/c
PP	6	Reader Run +	Out	20mA	active	Reader relay source.
RR	5				n/c
SS	4	Serial Output	Out	TTL	active	Raw TTL gate output.
TT	3	+5V	Out		passive
UU	2	Ground			passive
VV	1	Ground			passive