True Rms Ac Troubleshooting (Option -09); I/O Port Configurations; Service Position - Fluke 8842A Instruction Manual

8842A
Instruction Manual
PORT BIT
PO-0
PO-1
PO-2
PO-3
PO-4
PO-5
PO-6
PO-7
P2-0
P2-1
P2-2
P2-3
P2-4
P2-5
P2-6
P2-7
NOTES:
Due to external hardware conflicts, the following bits are NEVER driven by the Out-Guard C in
ANY diagnostic mode: P0-4,5,6,7; P2 (all bits); P3-1,2,3,4.
P3-6 is the 4 MHz clock for the NEC7210 IEEE chip (U901).
P3-7 is programmed as the serial output, and constantly transmits hex 55 every 820 s at 62,000
baud in all four diagnostic modes. This causes the front panel error message.

6-71. True RMS AC Troubleshooting (Option -09)

6-72. SERVICE POSITION

To provide easy access to the True RMS AC PCA and the Main PCA, the True RMS AC
PCA can be placed in the specially provided service position as follows:
1. Remove the case from the chassis using the Case Disassembly procedure provided
2. Release the four nylon latches that hold the True RMS AC PCA in place by pulling
3. Disconnect the red ac input lead from both the True RMS AC PCA and the Main
6-66
Table 6-25. I/O Port Configurations
CONFIGURATION
Static Read/Write
Dynamic
OUT
OUT
OUT
OUT
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
earlier in this section.
the latches upward. (See Figure 809-1E in Section 8.)
PCA.
PORT BIT
Address P1-0
Address P1-1
Address P1-2
Address P1-3
IN P1-4
IN P1-5
IN P1-6
IN P1-7
IN P3-0
IN P3-1
IN P3-2
IN P3-3
IN P3-4
IN P3-5
IN P3-6
IN P3-7
CONFIGURATION
Static Read/Write
Dynamic
OUT Data
OUT Data
OUT Data
OUT Data
OUT Data
OUT Data
OUT Data
OUT Data
IN IN
IN IN
IN IN
IN IN
IN IN
IN IN
Clock Clock
serial Serial