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Epson Research and Development Page 11
Vancouver Design Center
Interfacing to the NEC VR4102 / VR4111 Microprocessors S1D13708
Issue Date: 01/11/05 X39A-G-007-01
3.2 Host Bus Interface Signals
The Host Bus Interface requires the following signals:
• CLKI is a clock input which is required by the S1D13708 Host Bus Interface as a source
for its internal bus and memory clocks. This clock is typically driven by the host CPU
system clock. For this example, BUSCLK from the NEC VR4102/4111 is used for
CLKI.
• The address inputs AB[16:0], and the data bus DB[15:0], connect directly to the NEC
VR4102/4111 address bus (ADD[16:0]) and data bus (DAT[15:0]), respectively. CNF4
must be set to select little endian mode.
• Chip Select (CS#) must be driven low by LCDCS# whenever the S1D13708 is accessed
by the VR4102/4111.
• M/R# (memory/register) selects between memory or register accesses. This signal may
be connected to an address line, allowing system address ADD17 to be connected to the
M/R# line.
• WE1# connects to SHB# (the high byte enable signal from the NEC VR4102/4111)
which in conjunction with address bit 0 allows byte steering of read and write opera-
tions.
• WE0# connects to WR# (the write enable signal from the NEC VR4102/4111) and must
be driven low when the VR4102/4111 is writing data to the S1D13708.
• RD# connects to RD# (the read enable signal from the NEC VR4102/4111) and must be
driven low when the VR4102/4111 is reading data from the S1D13708.
• WAIT# connects to LCDRDY and is a signal output from the S1D13708 that indicates
the VR4102/VR4111 must wait until data is ready (read cycle) or accepted (write cycle)
on the host bus. Since VR4102/VR4111 accesses to the S1D13708 may occur asynchro-
nously to the display update, it is possible that contention may occur in accessing the
S1D13708 internal registers and/or display buffer. The WAIT# line resolves these
contentions by forcing the host to wait until the resource arbitration is complete.
• The Bus Status (BS#) and Read/Write (RD/WR#) signals are not used in this implemen-
tation of the NEC VR4102/4111 interface using the Generic #2 Host Bus Interface.
These pins must be tied high (connected to IO V
DD
).