The circuit is conventional. Control signals from the parallel port are applied to the 8 bit wide bus and in addition, some bi-directional control lines are also used. Four lines are used to return homing or limit switch information back to the host computer. The four limit switches can be attached to connector PL2 and are active low.
The input lines are pulled down by 6.8M resistors, probably intended to provide some anti-static resistance. All traffic to and from the parallel port is optically isolated by a combination of the 74HC14 inverters and thePC817 opto-isolators. Thereafter the signals are applied to the enable, clockwise/counterclockwise, and clock controls of the three TB6065AHQs. Other options are selectable in hardware via the DIP switches which are controlled as follows:


MOTOR CURRENT 	SWITCH 1 	SWITCH 2
100% 	ON 	ON
75% 	ON 	OFF
50% 	OFF 	ON
25% 	OFF 	OFF

DECAY MODE 	SWITCH 3 	SWITCH 4
FAST 	ON 	ON
25% DECAY 	ON 	OFF
50% DECAY 	OFF 	ON
100% DECAY 	OFF 	OFF

MICROSTEPPING 	SWITCH 5 	SWITCH 6
1 	ON 	ON
1/2 	ON 	OFF
1/16 	OFF 	ON
1/8 	OFF 	OFF

Other features of the circuit include the connector PL3 which can be fitted with jumpers to force pins 16 and 17 of the parallel port low. A relay RL1 and the associated transistor Q1 provide control of a high current to a further motor if required. The three CLOCK signals CLK1, CLK2 & CLK3 are monitored by Q3, Q4, & Q5 driving three LEDS D21, D25, & D31. These are visible on the top surface of the board near the power supply heat sink. Two other LEDs show the presence of the 5V and 12V supplies. A 15pin D socket and a SIL header provide access to signal points at ZA - ZJ on the schematic. These are probably intended to drive a proprietary display/control device but the author has no information on this at present.
The Schematic provides sufficient information to enable the stepper controller to be driven from any computer or microcontroller.

obvod je konvenn. dic signly z paralelnho portu jsou aplikovny na 8 bit sbrnice irok a navc jsou nkter bi-dc kontroln linie je tak pouvn. tyi dky jsou pouvny k nvratu navdc nebo koncov spna informace zpt do hostitelskho potae. tyi spnae mohou bt pipojeny do konektoru PL2 a jsou aktivn nzk.
Vstupn linky jsou taen dol 6.8M rezistory, pravdpodobn zamlel poskytovat nkter anti-statick odolnost. Veker provoz do az paralelnho portu je opticky izolovna kombinac 74HC14 mni a thePC817 opto-izoltory. Pot signly jsou aplikovny na povolen, ve smru hodinovch ruiek / proti smru hodinovch ruiek, a hodiny kontroly t TB6065AHQs. Jin monosti jsou voliteln v hardwaru prostednictvm pepnae DIP, kter jsou kontrolovny nsledujcm zpsobem:


MOTOR AKTULN SWITCH 1 SWITCH 2
100% ON
75% OFF
50% sleva na
25% OFF OFF

padkov reim SWITCH 3 Switch 4
FAST ON
25% DECAY ON OFF
50% OFF ON DECAY
100% DECAY OFF OFF

MIKROKROKOVN Switch 5 SWITCH 6
1 ON
1 / 2 ON OFF
1 / 16 OFF ON
1 / 8 OFF OFF

Dal vlastnosti obvodu pat konektor PL3, kter mohou bt vybaveny propojky nutit piny 16 a 17 paraleln port nzk. rel RL1 a souvisejc tranzistor Q1 poskytnout kontrolu nad vysokho proudu do dalho motoru v ppad poteby. Ti hodinov signly CLK1, CLK2 & CLK3 jsou sledovny 3. tvrtlet, Q4, Q5 a idisk temi LED kontrolkami D21, D25, D31 a. Tyto jsou viditeln na povrchu tabule v blzkosti tepelnho zdroje dezu. Dv jin LED diody ukazuj na ptomnost 5V a 12V zdroje. 15pin D zsuvky a zhlav SIL poskytuj pstup k signlu bod na ZA - ZJ na schmatu. Tito jsou pravdpodobn ureny k pohonu proprietrn displeje a ovldacch zazen, ale autor nem dn informace o tomto v souasn dob.
Schma poskytuje dostaten informace k tomu, aby krokov regultor bt zen z libovolnho potae nebo mikrokontrolrem.
