Appendix K: Parallel Interface Timing - Epson MX-70 User Manual

Appendix K
Parallel Interface Timing
The MX-70 includes a parallel interface as standard equipment, which is compatible to
the Centronics parallel interface. The Printer can be connected easily to any computer with
this interface structure. Fig, 3.1 shows the timing chart when signals are to be input from an
external device to the MX-70. As is apparent from the timing chart, when data are transmitted
to data lines DATA 1 through DATA 8 and the STROBE signal is generated by an external
device, the MX-70 sets the BUSY signal to "HIGH" level to inhibit the next data transfer from
the external device. The logical state of each data must be held as is until the BUSY signal
becomes "LOW" level again, after the transmission of the STROBE signal from the external
device, or Incorrect data may be written in the print buffer of the MX-70.
ACKNLG
STROBE
This timing chart also reveals that the ACKNLG signal from the MX-70 can be used in place
of the STROBE signal. This allows the Printer functions to be checked without use of a
special Instrument, in such a manner as described below.
STEP 1. Connect pin No. 1 (STROBE) to Pin No. 10 (ACKNLG) with a lead.
STEP 2. Connect pin Nos. 2 through 9 (DATA 1 through 8) of the interface connector as
required according to the character to be printed. For example, if character "A"
(represented by <41>H in ASCII code)
7 and 9, respectively to the ground (e.g., pin No. 19). Note that when pin Nos. 2
through 9 are left open without connecting them to the ground, data signals
become "HIGH" level and when they are connected to the ground, data signals
become "LOW" level.
BUSY
DATA
OµS (min.) 0.5µs (min.)
Fig. 3.1 Paralell Interface Timing
* D a t a s h o u l d b e h e l d
E a c h i s T T L l e v e l c o m p a t i b l e .
to be printed, connect pin Nos. 3, 4, 5. 6,
IS
APPENDIX K
d u r i n g t h e p e r i o d T
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