Fluke Biomedical 942A-200L-M4 - Manual (Page 30)

942A-200L-M4 & 942A-200L-M5 UDR
Operator Manual
2-16
Gross Counter (Read Only)
The gross counter is a 16-bit configuration. Octal buffer/drivers U40 (4004) and U41 (4006) interface the
low and high counter bytes to the data bus from U45 and U46 respectively. Dual module 16 counters
(U45, U46) accumulate counts from the signal processing circuitry over a program controlled sample
period and make this data available to the MPU. A high level on U45 pins 2 and 12, and U46 pins 2 and
12 cause the counters to clear in anticipation of a sample being initiated. A low level activates the
counters to accept pulses from the signal processing circuitry. Maximum count for a sample period is
32,768. When this count is achieved, U46 pin 8 goes high which causes the pulse counting to stop. This
condition is recognized by the MPU as an indication of counter overflow.
Sensitivity Select (Read Only)
Octal buffer U42 functions as an interface to provide the status of the sensitivity selection jumpers, mode
jumpers, anti-jam bit data, and serial data from E
2 PROM to the internal data bus and MPU. U42
responds to address 4008. The sensitivity read functions are listed in Table 2-14. The accuracy is shown
in Table 2-15.
Table 2-14. Sensitivity Select Read Functions
Data Bit Function
D0 Serial data from E
2
PROM
D1 Anti-Jam
D2 (Not used)
D3 JP3-5 (IN) Inhibit alarms during check source operation
(OUT) Alarms active during check source operation
D4 JP3-4 (IN) Fails in five minutes with no counts
(OUT) Does not fail
D5 JP3-3 (OUT) Auto alarm acknowledge, after counts return to normal
(IN) Manual Reset
D6 JP3-2 Sensitivity select; JP3 jumper IN MPU reads low (0)
JP3 jumper OUT MPU reads high (1)
D7 JP3-1 Sensitivity select: JP3 jumper IN MPU reads low (0)
JP3 jumper OUT MPU reads high (1)
Table 2-15. Sensitivity Selections (Accuracy)
JP3-1 JP3-2 Selection
IN IN Fixed 1 second update
IN OUT 10%
OUT IN 5%
OUT OUT 2%