Guarded Digital Control Circuitry - Fluke 5700A Series Service Manual

U5 with heat sink, bypass capacitors C10 and C28, and protection diodes CR9, CR10,
and CR12. Resistors R4 and R8 set the output voltage in the same manner as the +44S
supply. Capacitor C12 improves ripple rejection. Diodes CR9 and CR10 protect U5
against input shorts, while CR12 protects against reverse voltage.

2-77. Guarded Digital Control Circuitry

The Inguard CPU controls all the analog assemblies. It communicates with the
Unguarded CPU assembly (A20) through a serial fiber-optic link. The Inguard CPU is a
Hitachi 637A01Y0 CMOS microcontroller (U56) with 16K x 8 bit (16 KB, or 16
kilobyte) internal CMOS EPROM. Support circuitry includes 8K x 8 bits (8 KB) of
external CMOS static RAM, watchdog timer circuitry, reset and power glitch detect
circuitry, test switches, a serial fiber-optic link to the unguarded CPU, and decoders and
buffers to interface to the guarded digital bus. The assembly also generates an 8 MHz
sine wave for use by some of the analog assemblies.
2-78. Inguard CPU Memory Map
Table 2-11 shows the memory map of the Inguard processor.
Address Space (Hex)
0000 - 0027
0028 - 003F
0040 - 013F
0140 - 3FFF
4000 - 4007
4008 - 400F
4010 - 4017
4018 - 401F
4020 - 4027
4028 - 402F
4030 - 4037
4038 - 403F
4040 - 4047
4048 - 404F
4050 - 4057
4058 - 405F
4060 - 4067
4068 - 406F
4070 - 4077
4078 - 407F
4080 - 5FFF
6000 - 9FFF
A000 - BFFF
C000 - FFFF
2-79. Inguard Memory Configuration
The microcontroller (U56) has 16 KB (kilobytes) of internal EPROM program memory.
IC U62 provides 8 KB of external static CMOS RAM, with a jumper option for a plug-in
replacement with a 2 KB device.
Table 2-11. Inguard CPU Memory Map
Name
CS0*
CS1*
CS2*
CS3*
CS4*
CS5*
CS6
CS7*
CS8*
CS9*
CS10*
CS11*
CS12*
CS13*
CS14*
CS15*
Analog Section Detailed Circuit Description
Use
Internal Registers on the 6301
Unused memory space
Internal RAM 256 Bytes
Unused memory space
Wideband Output (A5)
Current/Hi-Res (A7)
Switch Matrix (A8)
Ohms Cal (A9)
Unused
DAC (A11)
DAC (A11)
Current/Hi-Res (A7)
Oscillator Control (A12)
Oscillator Output (A13)
High Voltage Control (A14)
Power Amplifier (A16)
Rear Panel (A21) Boost
Current/Hi-Res (A7)
Wideband Oscillator (A6) Unused
Unused
Unused(memory overlay of 4000-407F)
Unused
External RAM
Internal ROM or EPROM
Theory of Operation
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