Epson Research and Development
Page 15
Vancouver Design Center
Interfacing to the Motorola MPC821 Microprocessor
S1D13704
Issue Date: 01/02/12
X26A-G-010-03
4 MPC821 to S1D13704 Interface
4.1 Hardware Description
The interface between the S1D13704 and the MPC821 requires minimal glue logic. One
inverter is required to change the polarity of the WAIT# signal (an active low signal) to
insert wait states in the bus cycle. The MPC821 Transfer Acknowledge signal (TA) is an
active low signal which ends the current bus cycle. The inverter is enabled using CS# so
that TA is not driven by the S1D13704 during non-S1D13704 bus cycles. A single resistor
is used to speed up the rise time of the WAIT# (TA) signal when terminating the bus cycle.
BS# (bus start) is not used in this implementation and should be tied low (connected to
GND).
The following diagram shows a typical implementation of the MPC821 to S1D13704
interface.
Figure 4-1: Typical Implementation of MPC821 to S1D13704 Interface
MPC821
S1D13704
A[16:31]
D[0:15]
CS4
TA
WE0
WE1
OE
SYSCLK
RESET
AB15-AB0
DB[15:D0]
CS#
WAIT#
WE1#
WE0#
RD/WR#
RD#
BUSCLK
RESET#
Vcc
470
*