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CHAPTER 27
µ
PD78P078, 78P078Y
27.3 PROM Programming
The
µ
PD78P078 and 78P078Y each incorporate a 60-Kbyte PROM as program memory. To write a program
into the PROM make the device enter the PROM programming mode by setting the levels of the VPP and RESET
pins as specified. For the connection of unused pins, refer to 1.5 (2) PROM programming mode and 2.5 Pin
Configuration (Top Vew).
Caution Write the program in the range of addresses 0000H to EFFFH (specify the last address as
EFFFH). The program cannot be written by a PROM programmer in which the write address
cannot be specified.
27.3.1 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 device
is set to the PROM programming mode. This is one of the operating modes shown in Table 27-4 below according
to the setting of the CE, OE, and PGM pins.
The PROM contents can be read by setting the read mode.
Table 27-4. PROM Programming Operating Modes
Pin
Operating mode
Page data latch 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
LxHH
xLL
Read L L H Data output
Output disabled +5 V +5 V L H x High impedance
Standby H x x High impedance
x: 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
PD78P078s or 78P078Ys are connected to the data bus, data can be read from any
one device by controlling the OE pin.
RESET VPP VDD CE OE PGM D0 to D7
Program inhibit High impedance
+12.5 V +6.5 V