Mindray Passport 5-Lead, Service Manual

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Block Diagrams Theory of Operation
2 - 22 0070-00-0420 Passport 5-Lead, 5L, LT, XG Service Manual
FIGURE 2-12
Data Acquistion System Block Diagram
Port A Function
The outputs in port A are controlled by the software. The software supports a command
format in which groups of 4 bits can be changed. The lower four bits of port A contain all of
the temperature mode control lines. When a temperature mode control command is received
by the microcontroller, the four bits of data imbedded in this command are asserted on the
lower 4 bits of port A. These four signals are then used by the temperature block to control
analog switches. The upper 4 bits of port A support the ECG function. Upon receipt of an
ECG mode control command, the microcontroller asserts the 4 data bits contained in the
command on the upper 4 bits of port A. The lead select lines pass directly to the ECG block,
while the reset and filter lines are level-shifted, without inversion, by dual comparator U37
and associated pullup resistors, which provide a nominal rail-to-rail swing between the +7.5
and -7.5 volt supplies. The +2.5 volt supply, which is at the midpoint of the logic swing, is
used as the comparator’s reference. Diode D41 allows ORing of the reset signal originating
at the microcontroller with that generated by the ECG subsystem internally. Resistor R249
provides isolation between the comparator and the 2.5 volt supply.
A
n
a
log
I
n
pu
ts
Por
t C
Por
t D
Po
rt
A
Level
Shift
A/D Converter
Input
Networks
Buffer
Buffer
O
p
to
-I
s
o
la
to
rs
U42
U43
U44
Q10,U36
U39
U37
Isolated
Microcontroller
Divider
3.686 MHz
U40
+5
Level
Shift
Select
I/O Clock
Data
+7.5v Test
2.5v Test
ECGI/II/III
Resp Mon
Press 1
Press 2
Temp
Respen*
0
1
5
6
7
Por
t B
0
1
2
3
4
5
7
6
3
2
1
0
SCK
MISO
MOSI
SS
TDO
RDI
Reset
TD
TC
TB
TA
Resprst
5
4
Lead Sel 0
Lead Sel 1
NON-ISOLATED
Mux
Address
Respflt
115 KHZ
Data Acquisition Subsystem
6
7
ESU Noise
ARST
Filter
Q11,Q13
Buffer
ECGVA
ECGII
+5/-7.5V TEST
TXDA
RXDB
RESET*
U36
U38
T Flag
Hi-Z
Lead Fault
P Trigger
E Trigger
Q12 1.84MHz