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Vancouver Design Center
S1D13505 Interfacing to the NEC VR4102/VR4111 Microprocessors
X23A-G-007-06 Issue Date: 01/02/05
3 S1D13505 Host Bus Interface
The S1D13505 directly supports multiple processors. The S1D13505 implements a 16- bit
MIPS/ISA Host Bus Interface which is most suit able for direct connection to the
VR4102/VR4111 microprocessor.
The MIPS/ISA host bus interface is selected by the S1D13505 on the rising edge of
RESET#. After releasing reset the bus interface signals assume their selected conf iguration.
For details on S1D13505 configuration, see Section 4.2, S1D13505 Hardware Configu-
ration on page 13.
Note
At reset, the Host Interface Disable bit in the Miscellaneous Disable Register
(REG[1Bh] bit 7) is set to 1. This means that only REG[1Ah] (read-only) and
REG[1Bh] are accessible until a write to REG[1Bh] sets bit 7 to 0 making all regis-
ters accessible. When debugging a new hardware design, this can sometimes give the
appearance that the interface is not working , so it is important to remember to clear this
bit before proceeding with debugging.
3.1 Host Bus Interface Pin Mapping
The following table shows the functions of each host bus interface signal.
Table 3-1: Host Bus Interface Pin Mapping
S1D13505 Pin Name NEC VR4102/VR4111 Pin Name
AB20 ADD20
AB[19:0] ADD[19:0]
DB[15:0] DAT[15:0]
WE1# SHB#
M/R# ADD21
CS# LCDCS#
BUSCLK BUSCLK
BS# Connected to VDD
RD/WR# Connected to VDD
RD# RD#
WE0# WR#
WAIT# LCDRDY
RESET# connected to system reset