Fluke Biomedical 960CI-200 - Manual (Page 12)

Theory of Operation
4
4-2
4.5 Address Decoding
The address decoding is done by U9, U8, U11, and U6. Logic array U6 is programmed to provide the following enable
signals:
ACIA1
- for address 300 through 3FF
ACIA2 - for address 400 through 4FF
ACIA3 - for address 500 through 5FF
RAM1 - for memory RAM 2000 – 3FFF
RAM2 - for memory RAM 4000 – 5FFF
RAM3 - for memory RAM 6000 – 7FFF
PROM - for memory PROM 8000 – FFFF
U6 provides a control signal to the internal data bus transceiver to route data to and from memory to the processor.
Under a READ command the processor reads from memory. Under a WRITE command the processor writes to
memory. U9 provides the CHAN ID signal that enables U15 and read the channel identification.
4.6 Communication Loops
The 960CI-200 has three communication loops. Loops 1 and 2 are used for two-way communications with the
computer, while loop 3 is a receive only one-way communications loop to the monitor.
Only loop 1 will be discussed here since loop 2 circuitry is identical in operation. (ACIA1, U16 is loop 1) & (ACIA2, U17
& Z9 is loop 2). The ACIA’s have the following signal inputs and outputs:
CONTROL: T2 L02 R/W, A0, UB BIT RATE, ACIA 1,2,3, IRQ, and UB BIT RATE (determines data baud rate)
DATA: Parallel D0 through D7, Serial TX & Serial RX, T2, 02. All data transfers occur on falling edge
of 02.
R/W: HI for read and LO for write operations.
A0: Part of the address decoding, A0 = 0 for data and A0 = 1 for control
ACIA 1,2,3: Selected when low
IRQ: Output that goes to the processor to cause an interrupt when receiving data and the
buffer is full.
D0 – D7: Parallel data bus (internal data bus)
TX: Transmit (Serial data)