Fluke Biomedical 960SF-220 - Manual (Page 10)

Victoreen 960SF-220,221,230,231
Operators Manual
2-2
2.5 Address Decoding Circuits
Device selection is set by a jumping option on SW1 or SW2. Input signals for decoding are DS, 02, R/W,
A0, A 1, and A2. These input signals are inverted through Z36 and Z37 and fed into Z27 and Z28 that are
decoders. Z27 decodes for READ ONLY registers and Z28 decodes for WRITE ONLY registers. The
decoding scheme is shown in Table 2-1.
Table 2-1. Address Decoding
A2 A1 A0 R/W DS Function Enable Signal
0 0 0 1 1
COUNTER HIGH
BYTE
READ 0
0 0 1 1 1
COUNTER LOW
BYTE
READ 1
0 1 0 1 1 A/D UPPER BITS READ 2
0 1 1 1 1 SCALER STATUS READ 3
1 0 0 1 1 A/D LOWER 4 BITS READ 4
0 0 0 0 1 RELAYS WRITE 0
0 0 1 0 1 SCALER CONTORL WRITE 1
0 1 0 0 1 LAMPS WRITE 2
0 1 1 0 1 D/A CONVERTER WRITE 3
1 0 0 0 1 MPU RESET WRITE 4
x x x 0 1 - WRITE
x x x 1 1 - READ
2.6 Bus Transceivers
Z31 and Z30 are data bus transceivers transferring data from the scaler to the external data bus when
READ is active (high) and from the external data bus to the scale when WRITE is active (low).
2.7 Lamp Drivers
Z32 is a WRITE only register used for lamps. It clocks the data in when WRITE 2 is active (low). Z23 is a
Darlington array driving the front panel ALARM, WARN, and FAIL lamps. The FAIL lamp is handled
through watchdog timer Z38 that is set for 5 seconds. If the fail light is not written to every 5 seconds or
sooner, it will go off to indicate failure and also provide a pulse to watchdog pin 72 on J1.
2.8 Relay Drivers
Z29 is a WRITE only register used for relays. It clocks data in when WRITE 0 is active (low). Z18 is a
Darlington array capable of switching +24 VDC at up to 150 mA with all outputs
energized
simultaneously.