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800961-C Nov. 2000
İYİALLINCERODT
RAM Operation
The RAM (U15) is socketed so that it can handle any JEDEC
standard 32K x 8-bit, 64K x 8-bit or 128K x 8-bit RAM.
The socket
will be 32-pin to accommodate the 128K x 8-bit device.
If a smaller
(28-pin) RAM is used it should use the lower portion of the socket
(i.e. pin 1 of the device = pin 3 of the socket).
Note that the chip
select line is tied to the output enable line, which means that the
outputs will be enabled for both reads and writes.
However, during
a write operation, the output enable is a "don't care" input.
EPROM Operation
Any JEDEC standard 64K x 8-bit or 128K x 8-bit EPROM may be
used in the sockets occupied by U10 and U12. The CPU system
will boot from EPROM U10. Therefore, if only one EPROM is used,
it must be placed in U10.
Digital to Analog Converter Operation
U18 is the Digital to Analog Converter (DAC) chip.
It is a 12-bit
DAC with a full 12-bit interface to the microprocessor.
An RC network (R37, C21, C9) is connected to the REFOUT pin in
order to provide decoupling for the internal voltage reference.
The DAC uses a +12 V supply. This is the only chip on the CPU
board that uses +12 V. The output range is jumper configurable as
Oto +5 VorOto +10 V.
Itis hardwired for O to +5 V. The output
code is natural binary with 1 LSB defined as follows:
For 0 V to +10 V Range:
1 LSB = Vy (1/2048) = 2.44 mV
For 0 V to +5 V Range:
1 LSB = Vy (1/4096) = 1.22 mV
Analog to Digital Converter Operation
U16 is the Analog to Digital Converter (ADC) chip.
It is an 8-chan-
nel, 8-bit ADC.
The microprocessor uses the Serial Peripheral
Interface (SPI) bus to communicate with the DAC.
The input range is O to +5 V. The inputs are protected by 4.7 ký
resistors (R24-R30, R36).
The output code is natural binary with 1 LSB defined as follows:
1 LSB = FS/256 = (5/256)V = 19.5 mV
A conversion is started when the microprocessor reads one of the
eight channels.
When the INT line goes low an interrupt is gener-
ated on microprocessor IRQ3.
Another read of the same channel
will contain valid conversion data.
Jumpers and LED's
Jumpers and LED's are for Liebel-Flarsheim testing use only.
3-21
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