2-77. Guarded Digital Control Circuitry

Theory of Operation 2

Analog Section Detailed Circuit Description

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

Table 2-11. Inguard CPU Memory Map

Name

Use

 

 

 

Internal Registers on the 6301

 

Unused memory space

 

Internal RAM 256 Bytes

CS0*

Unused memory space

CS1*

Wideband Output (A5)

CS2*

Current/Hi-Res (A7)

CS3*

Switch Matrix (A8)

CS4*

Ohms Cal (A9)

CS5*

Unused

CS6

DAC (A11)

CS7*

DAC (A11)

CS8*

Current/Hi-Res (A7)

CS9*

Oscillator Control (A12)

CS10*

Oscillator Output (A13)

CS11*

High Voltage Control (A14)

CS12*

Power Amplifier (A16)

CS13*

Rear Panel (A21) Boost

CS14*

Current/Hi-Res (A7)

CS15*

Wideband Oscillator (A6) Unused

 

Unused

 

Unused(memory overlay of 4000-407F)

 

Unused

 

External RAM

 

Internal ROM or EPROM

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.

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Fluke 5720A service manual Guarded Digital Control Circuitry, Inguard CPU Memory Map, Inguard Memory Configuration