Tandy 1000 HX Technical Reference Manual page 307

• TANDY COMPUTER PRODUCTS
SIGNAL DESCRIPTIONS
The following signals function the same on the M68C45
Megacells and on the standard VL6845 family of CRT
Controller ICs.
Description
Register Select
Enable
Specify READ (high) or WRITE (low)
operation
Chip (6845 megacell) select, low true
Character Clock
Not Used
Data Bus
Raster Address
Horizontal Sync
Reset, low true
The following signals are unique to the VE68C45 Megacells,
or are functionally different on the VE68C45 Megacells and
the VL6845 ICs.
38
Signal
RS
E
RNW
CSB
CCLK
LPSTB
D0-D7
RA0-RA4
HS
RESETB
I/O
IP
IP
IP
IP
IP
IP
I/O
OP
OP
IP
Description
Register Select
Enable
Specify READ (high) or WRITE (low)
operation
Chip (6845 megacell) select, low true
Character Clock
Not Used
Data Bus
Raster Address
Horizontal Sync
Reset, low true
Signal
DE
CURSOR
VS
I/O
OP
OP
OP
Description
Display Enable output - active (DE =
"1") when the VE68C45 is generating
active display information. The S
version can be programmed with a 0,
1, or 2 character delay. The SY
version can be programmed for a 0 or
1 character delay.
Cursor output - this signal is high
when the raster scan coincides with
the programmed cursor position. The
S version can be programmed with a 0,
1, or 2 character delay. The SY
version can be programmed for a 0 or
1 character delay.
Vertical Sync output - active high
pulse which determines the vertical
placement of the video data. An
optional feature permits programming
the Vertical Sync pulse width.