Printer Port Control Register - Motorola MVME1X7P Programmer's Reference Manual

Printer Port Control Register

ADR/SIZ
BIT
7
NAME
OPER
R
RESET
0
MAN
FAST
Note
STB
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$FFF42037 (8 bits)
6 5
DOEN
R R R/W
0 0 0 PL
Manual Strobe Control - This bit selects the auto or
manual mode for the printer strobe. When this bit is low,
the printer strobe is generated automatically by a write to
the Printer Data Register (auto mode). When this bit is
high, the strobe pin is directly controlled by the STB
control bit (manual mode).
Strobe Timing - In auto mode, this bit controls the printer
strobe timing. When this bit is low, the strobe time is 212
BCLK periods (10.6 s at 20MHz, 8.5 s at 25MHz and
6.4 s at 33MHz). When this bit is high, the strobe time is
50 BCLK periods (2.5 s at 20MHz, 2 s at 25MHz and
1.5 s at 33MHz). Note that the strobe time is the width of
the low-going pulse generated on the STB* pin. Also note
that after a write to the Printer Data Register, the
PCCchip2 delays about one strobe time before issuing the
STB* pulse. This bit is not used in manual mode.
The PCCchip2 runs at half the MPU speed on the
MVME177P. For example, an MVME177P with a 50 MHz
MPU will run the PCCchip2 at 25 MHz.
Manual Strobe Control - In the manual mode, the software
controls the strobe timing. When this bit is high, the
printer strobe is activated. When this bit is low, the printer
strobe is not activated. This bit has no function in auto
mode.
4 3 2
INP STB
R/W R/W
0 PL 0 PL
Programming Model
1 0
FAST MAN
R/W R/W
0 PL 0 PL
3-45
3