Fluke Biomedical 942A-200L-M4 - Manual (Page 24)

942A-200L-M4 & 942A-200L-M5 UDR
Operator Manual
2-10
Write Register Decoding
Decoding for write registers within the main circuit board is performed by U2, which is a 1 of 8 decoder.
Control signals for U2 are /REGSELECT, /R/W (active high), /WRITE02 as well as addresses A1, A2, and
A3. U2 decodes two addresses per output, starting at 4000, and ending with 400E. These outputs are
active low. Table 2-4 lists write registers, their assigned function and address.
Address State
A3 A2 A1
Hex
Address
Function
0 0 0 4000 Status Indicators
0 0 1 4002 E
2
PROM
0 1 0 4004 D/A Converter
0 1 1 4006 Display Control
1 0 0 4008 Display Data
1 0 1 400A Counter Control
1 1 0 400C Relay Control
1 1 1 400E (Spare)
Table 2-4. Write Register Functions
The following paragraphs describe the operation of each of these registers.
Counter Control (Write Only)
The counter control register (U43) is an 8-bit register with clear, and responds to address 400A. Upon
initial power-up, the system resets all outputs low. Table 2-5 lists the counter control register write
functions.
NOTE
Data written into U43 remains at the outputs until a reset
occurs or new data is written.
Table 2-5. Counter Control Register Write Functions
Data Bit Function
D0 COUNTER CLEAR
D1 COUNTER ENABLE
D2 HV SHUTDOWN
D3 HV SELECT (used to digitize HV)
D4 /CLEAR SWITCH LATCH
D5 Not Used
D6 Not Used
D7 Not Used