NEC NEC PD78081(A), User Manual

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CHAPTER 15
µ
PD78P083
RESET V
PP
V
DD
CE OE PGM D0-D7
15.2 PROM Programming
The
µ
PD78P083 incorporate a 24-Kbyte PROM as program memory, respectively. To write a program into
the
µ
PD78P083 PROM, make the device enter the PROM programming mode by setting the levels of the V
PP
and RESET pins as specified. For the connection of unused pins, see paragraph (2) “PROM programming
mode” in section 1.5 Pin Configuration (Top View).
Caution Perform program writing only in the 0000H to 5FFFH address range (specify the last address
as 5FFFH.)
The program cannot be correctly written by a PROM programmer which does not have a write
address specification function.
15.2.1 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
PD78P083
are set to the PROM programming mode. This is one of the operating modes shown in Table 15-3 below according
to the setting of the CE, OE, and PGM pins.
The PROM contents can be read by setting the read mode.
Table 15-3. PROM Programming Operating Modes
Pin
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 +5V L L H Data output
Output disabled L H
×
High impedance
Standby H
× ×
High impedance
Remark
×
: L or H
(1) Read mode
Read mode is set by setting CE to L and OE to L.
(2) Output disable mode
If OE is set to H, data output becomes high impedance and the output disable mode is set.
Therefore, if multiple
µ
PD78P083s are connected to the data bus, data can be read from any one device by
controlling the OE pin.