
DESCRIPTION
7902 Group User’s Manual
1-5
Apply 5 V ± 0.5 V to pin Vcc and 0 V to pin Vss.
This pin switches the operating mode.
Note: When MD1 = Vss and MD0= Vss, the microcomputer starts
operation in the single-chip mode after reset. It’s processor
mode can be switched to the memory expansion or
microprocessor mode by software.
The microcomputer is reset when “L” level is input to this pin.
Pins XIN and XOUT are the input and output pins of the clock
generating circuit, respectively. Connect these pins via a
ceramic resonator or a quartz-crystal oscillator. When an
external clock is input, this clock should be input to pin XIN,
and pin XOUT should be left open.
The input level to this pin determines whether the external
data bus has a 16-bit width or an 8-bit width. A 16-bit width
is selected when the input level = Vss, and an 8-bit width is
selected when the input level = Vcc. When BYTE = Vss, by
software, the external data bus width can be set to 8 bits for
each of areas CS1 to CS3.
This is the input pin for the NMI interrupt. While pin RESET
is at “L” level or after reset, this pin is pulled up. This pullup
state can be removed by software.
To use the PLL frequency multiplier, be sure to connect this
pin to the filter circuit.
The power source input pin for the A-D and D-A converters.
Connect this pin to pin Vcc.
The power source input pin for the A-D and D-A converters.
Connect this pin to pin Vss.
This is the reference voltage input pin for the A-D and D-A converters.
1.3 Pin description
Single-chip mode (Note),
Memory expansion mode,
Microprocessor mode
Boot mode
Flash memory parallel I/O mode
—
Input
Output
Input
—
Input
Input/Output
Power source input
MD0
MD1
Reset input
Clock input
Clock output
External data bus
width select input
NMI interrupt input
Filter circuit connection
Analog power source
input
Reference voltage input
Vcc, Vss
MD0
MD1
RESET
XIN
XOUT
BYTE
NMI
VCONT
AVcc
AVss
VREF
1.3 Pin description
Tables 1.3.1 to 1.3.4 list the pin description.
Table 1.3.1 Pin description (1)
Name
Pin
Function
Vss
Vcc
Vss
Vcc
MD1
Vss
Vcc
MD0
Operating mode