HARDWARE
1-78
38B7 Group User’s Manual
FUNCTIONAL DESCRIPTION
FLASH MEMORY MODE
The M38B79FF has the flash memory mode in addition to the nor-
mal operation mode (microcomputer mode). The user can use this
mode to perform read, program, and erase operations for the in-
ternal flash memory.
The M38B79FF has three modes the user can choose: the paral-
lel input/output and serial input/output mode, where the flash
memory is handled by using the external programmer, and the
CPU reprogramming mode, where the flash memory is handled by
the central processing unit (CPU). The following explains these
modes.
(1) Flash memory mode 1 (parallel I/O mode)
The parallel I/O mode can be selected by connecting wires as
shown in Figures 85 and supplying power to the VCC and VPP
pins. In this mode, the M38B79FF operates as an equivalent of
MITSUBISHI’s CMOS flash memory M5M28F101. However, be-
cause the M38B79FF’s internal memory has a capacity of 60
Kbytes, programming is available for addresses 0100016 to
0FFFF16, and make sure that the data in addresses 0000016 to
00FFF16 and addresses 1000016 to 1FFFF16 are FF16. Note also
that the M38B79FF does not contain a facility to read out a device
identification code by applying a high voltage to address input
(A9). Be careful not to erratically set program conditions when us-
ing a general-purpose PROM programmer.
Table 12 shows the pin assignments when operating in the paral-
lel input/output mode.
Table 12 Pin assignments of M38B79FF when operating in
the parallel input/output mode
VCC
VPP
VSS
Address input
Data I/O
__
CE
___
OE
___
WE
M38B79FF
VCC
CNVSS
VSS
Ports P0, P1, P31
Port P2
P36
P37
P33
M5M28F101
VCC
VPP
VSS
A0–A16
D0–D7
__
CE
__
OE
___
WE
Functional Outline (parallel input/output mode)
In the parallel input/output mode, the M38B79FF allow the user to
choose an operation mode between the read-only mode and the
read/write mode (software command control mode) depending on
the voltage applied to the VPP pin. When VPP = VPPL, the read-
only mode is selected, and the user can choose one of three
states (e.g., read, output disable, or standby) depending on inputs
___ ___
___
to the CE, OE, and WE pins. When VPP = VPPH, the read/write
mode is selected, and the user can choose one of four states
(e.g., read, output disable, standby, or write) depending on inputs
__
___
to the CE, OE, and WE pins. Table 13 shows assignment states of
control input and each state.
q Read
__
The microcomputer enters the read state by driving the CE, and
__
___
OE pins low and the WE pin high; and the contents of memory
corresponding to the address to be input to address input pins
(A0–A16) are output to the data input/output pins (D0–D7).
q Output disable
The microcomputer enters the output disable state by driving the
__
___
__
CE pin low and the WE and OE pins high; and the data input/out-
put pins enter the floating state.
q Standby
__
The microcomputer enters the standby state by driving the CE pin
high. The M38B79FF is placed in a power-down state consuming
only a minimal supply current. At this time, the data input/output
pins enter the floating state.
q Write
The microcomputer enters the write state by driving the VPP pin
___
__
high (VPP = VPPH) and then the WE pin low when the CE pin is
__
low and the OE pin is high. In this state, software commands can
be input from the data input/output pins, and the user can choose
program or erase operation depending on the contents of this soft-
ware command.
Pin
Mode
Read
Output disable
Standby
Read
Output disable
Standby
Write
Read-only
Read/Write
__
CE
VIL
VIH
VIL
VIH
VIL
VIH
×
VIL
VIH
×
VIH
Table 13 Assignment states of control input and each state
__
OE
___
WE
VIH
×
VIH
×
VIL
VPPL
VPPH
VPP
Output
Floating
Output
Floating
Input
Data I/O
Note:
× can be VIL or VIH.
State