CHAPTER 19
µ
PD78P0208
375
User’s Manual U11302EJ4V0UM
19.3 PROM Programming
The
µ
PD78P0208 incorporates a 60 KB PROM as program memory. When programming, the PROM
programming mode is set by means of the V
PP
pin and the RESET pin. For the connection of unused pins, refer
to
1.5 Pin Configuration (Top View) (2) PROM programming mode
.
Caution
Programs must be written in addresses 0000H to EFFFH (the last address EFFFH must be
specified). Programs cannot be written by a PROM programmer that cannot specify the write
address.
19.3.1 Operating modes
When +5 V or +12.5 V is applied to the V
PP
pin and a low-level signal is applied to the RESET pin, the
µ
PD78P0208 is set to the PROM programming mode. This is one of the operating modes shown in Table 19-
4 below according to the setting of the CE, OE, and PGM pins.
The PROM contents can be read by setting the read mode.
Table 19-4. PROM Programming Operating Modes
Pin
RESET
V
PP
V
DD
CE
OE
PGM
D0 to D7
Operating Mode
Page data latch
L
+12.5 V
+6.5 V
H
L
H
Data input
Page write
H
H
L
High impedance
Byte write
L
H
L
Data input
Program verify
L
L
H
Data output
Program inhibit
×
H
H
High impedance
×
L
L
Read
+5 V
+5 V
L
L
H
Data output
Output disabled
L
H
×
High impedance
Standby
H
×
×
High impedance
×
: L or H
(1) Read mode
Read mode is set by setting CE to L and OE to L.
(2) Output disabled mode
If OE is set to H, data output becomes high impedance and the output disabled mode is set.
Therefore, if multiple
µ
PD78P0208s are connected to the data bus, data can be read from any one device
by controlling the OE pin.
(3) Standby mode
Setting CE to H sets the standby mode.
In this mode, data output becomes high impedance irrespective of the status of OE.