APPENDIX K
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.
BUSY
ACKNLG
DATA
STROBE
* D a t a s h o u l d b e h e l d d u r i n g t h e p e r i o d T
E a c h i s T T L l e v e l c o m p a t i b l e .
OµS (min.) 0.5µs (min.)
Fig. 3.1 Paralell Interface Timing
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) IS to be printed, connect pin Nos. 3, 4, 5. 6, 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.