Mindray Passport 5-Lead, Service Manual

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Block Diagrams Theory of Operation
2 - 60 0070-00-0420 Passport 5-Lead, 5L, LT, XG Service Manual
Address Decoder
The 80C196 address decoding is controlled by an EP320 EPLD (U7). Two different decoding
is possible, depending on the state of the signal PIB (OPT2). In the module mode, PIB is high.
In the module mode, (module mode = DSBP module used in any product other than
ACCUTORR 3/4) when the bank bit BANK, (U5 pin 33) is set high, the lower 32K bytes (0-
32K) are mapped to the on-board EPROM; the next 8K bytes (32K-40K) are mapped to non-
volatile RAM; the next 16K bytes (40K-56K) are not used; and the last 8K bytes (56K-64K)
are mapped to I/O, the only I/O available being the quad DAC, U9.
When the bank bit is set low, the lower 8K bytes (0K-8K) are still mapped to the on-board
EPROM; but the next 24K (8K-32K) bytes are mapped to nonvolatile RAM; the remaining
RAM and I/O space remain the same.
The address decoder EPLD, U7 also disables the pump when the overpressure condition
OVPR is set and buffers the reset signal to the 80C196 microcontroller.
The Pressure and Pulse Channel Amplifiers
The normal pressure transducer installed is a Sensym BP01. The output of the pressure
transducer is amplified by an instrumental amplifier implemented by U13A, C, and D. The
gain can be adjusted by trimpot VR1. The output is then buffered, low pass filtered and offset
adjusted by U13B and sent to the 80C196 A/D channel 7 at the pressure signal. The offset
is automatically corrected by adjusting the voltage level of OFFSET from the output channel 1
of the quad DAC U9. The gain of the amplifier is such that the output at U13 pin 7 is about
68.27mmHg/V.
The pulse channel signal is obtained by AC coupling and amplifying the pressure signal
(U13B-7). The pulse channel output can be reset by activating the CLEAR signal. This signal
can be activated when there is disturbance at the pulse output during pneumatic switch-overs
or severe motion artifacts. There are two gain switches controlled by U8A and U8B,
implementing four possible gain settings. The nominal gain settings for the pulse channel are
about 28, 56, 111, or 222. The default gain for adult mode is 28 and the default gain for
neonate mode is 111. The pulse signal is connected to the 80C196 A/D channel 5.
U11, U21B and U21C are not used at this time.
Reference vo5VR and -5VR are generating by amplifying a 2.5V reference generator
U12 by a factor of 2 and -2 respectively.
The sampling rate of the 80C196 A/D is about 250 Hz.