Epson MFJ-1278B Specifications, General Description, Detailed Circuit Description, Hdlc Frames

MFJ-1278B MULTI-MODE	TABLE OF CONTENTS
Link Status Messages		302
MFJ-1278B SPECIFICATIONS		305
GENERAL DESCRIPTION		306
DETAILED CIRCUIT DESCRIPTION		307
Oscillator		307
Dividers and Baud-rate Generator		307
CPU Complex		308
Serial Interface		308
Watch-dog Timer		309
Modem		309
Power Supply		309
RS-232C HANDSHAKING PROTOCOL		310
JUMPER FUNCTIONS		312
PARALLEL PRINTER PORT PIN FUNCTION,J12		315
TTL INTERFACE PORT PIN FUNCTION,J5		316
MULTI-LEVEL INTERFACE CONNECTOR,J13		317
EXTERNAL MODEM INTERFACE CONNECTOR - J14		317
MODEM DISCONNECT HEADER, J4		318
HF TUNING INDICATOR		320
GENERAL TESTS		321
Step 1: Power Supply		322
Step 2: Obvious Problems		322
Step 3: Assembly Problems		322
Step 4: Cabling Problems		323
SPECIFIC SYMPTOMS		323
Symptom: TNC appears dead		323
Oscillator and Reset Circuits		323
Digital Logic Lines		323
Symptom: Modem won't calibrate or key transmitter		324
Symptom: Uncopyable transmitted or received packets		325
TERMINAL INTERFACE TROUBLESHOOTING		325
Symptom: MFJ-1278B won't sign on to the terminal		325
Symptom: The MFJ-1278B appears to be signing on but only gibberish is
printed on the terminal		326
Symptom: The MFJ-1278B signs on OK but won't accept commands		326
Symptom: The MFJ-1278B appears to have "lock-up" i.e. not responding to any
commands		326
EXPLANATION OF PROTOCOL		327
Physical Layer		327
Data Link Layer		327
HDLC FRAMES		328
AX.25 LEVEL TWO		329