DMP 300  (260-2818)    Parallel Interface Signals       Faxback Doc. # 4631


PIN #   │  SIGNAL        │SIGNAL DIRECTION      │       FUNCTION
────────┼────────────────┼──────────────────────┼─────────────────────────────
  1     │DATA STROBE     │TO PRINTER            │Samples the input data when
        │                │                      │changing from low to high.
  2     │DATA BIT 1      │─┐                    │
  3     │DATA BIT 2      │ │                    │
  4     │DATA BIT 3      │ │                    │Indicates the input data.
  5     │DATA BIT 4      │ │                    │High level signal shows a 1,
  6     │DATA BIT 5      │ >> TO PRINTER        │and low level signal shows
  7     │DATA BIT 6      │ │                    │a 0.
  8     │DATA BIT 7      │ │                    │
  9     │DATA BIT 8      │─┘                    │
 10     │ACKNOWLEDGE     │FROM PRINTER          │At a low level, indicates
        │                │                      │that a character input is
        │                │                      │complete or that a function
        │                │                      │operation is finished.
        │                │                      │
 11     │BUSY            │FROM PRINTER          │At a high level, data recep-
        │                │                      │tion is impossible. At a low
        │                │                      │level, data reception is
        │                │                      │possible.
        │                │                      │
 12     │PAPER END       │FROM PRINTER          │At a high level, indicates
        │                │                      │paper end.
        │                │                      │
 13     │BUSY-N          │FROM PRINTER          │Tandy Mode: At a low level,
        │                │                      │data reception is impossible.
        │                │                      │At a high level, data recep-
        │                │                      │tion is possible.
        │                │                      │
        │SELECT          │FROM PRINTER          │*IBM Mode: at a high level,
        │                │                      │indicates that the printer
        │                │                      │is in select mode (data
        │                │                      │reception possible).
        │                │                      │
14      │NC              │                      │Tandy mode
        │AUTO LF-N       │                      │*IBM mode
        │                │                      │
16      │0V              │                      │
17      │CHASSIS         │                      │
        │GROUND          │                      │
        │FRAME           │                      │
        │GROUND          │                      │
        │                │                      │
18      │+5V             │FROM PRINTER          │Tandy Mode: +5V power supply
        │                │                      │(Max. 50 mA)
        │NC              │                      │*IBM mode
        │                │                      │
19-30   │0V              │                      │Twisted pair return (for pins
        │                │                      │# 1 through 11).
 31     │NC              │                      │Tandy mode
        │INPUT PRIME-N   │TO PRINTER            │*IBM Mode:When this goes low,
        │                │                      │the printer control section
        │                │                      │is initialized. The low level
        │                │                      │period should be more than
        │                │                      │0.5ms.
        │                │                      │
 32     │FAULT-N         │FROM PRINTER          │This signal goes from high to
        │                │                      │low level when paper runs out
        │                │                      │
 33     │INIT-N          │TO PRINTER            │Tandy Mode: When this goes
        │                │                      │low, the printer control sec-
        │                │                      │tion is initialized. The low
        │                │                      │level period should be more
        │                │                      │than 0.5ms.
        │                │                      │*IBM Mode: 0V
        │                │                      │
 15,34  │NC              │                      │Unused pin (No connection)
        │                │                      │
 35     │NC              │                      │Tandy Mode
        │Pulled High     │                      │*IBM Mode
        │                │                      │
 36     │NC              │                      │Tandy Mode
        │SLCT IN-N       │                      │*IBM Mode
────────┴────────────────┴──────────────────────┴─────────────────────────────

* IBM interface mode is achieved by moving jumpers located inside the printer. 
See you local Radio Shack Service Center for this change.


(smm 07/27/93)