UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 624

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

21.1.3 Basic Operation of Local Bus Interface
bus (A8 to A19). When the local bus interface is used, P64, P65 and port 4 automatically operate as RD, WR and AD0
to AD7 (in the PD784021, these operate only as RD, WR and AD0 to AD7 at all times). On the address bus, only the
pins that correspond to the extension memory size operate as address bus pins.
584
The local bus interface accesses external memory using ASTB, RD, WR, an address/data bus (AD0 to AD7) and address
An outline of the memory access timing is shown in Figures 21-6 and 21-7.
* The number of address bus pins used depends on the extension mode size.
* The number of address bus pins used depends on the extension mode size.
AD0 - AD7 (Output)
ASTB (Output)
RD (Output)
ASTB (Output)
AD0 - AD7
A8 - A19*
WR (Output)
(Output)
A8 - A19*
(Output)
Hi-Z
Hi-Z
CHAPTER 21 LOCAL BUS INTERFACE FUNCTION
Address (Output)
Low-Order Address
Low-Order
Figure 21-6 Read Timing
Figure 21-7 Write Timing
Hi-Z
Hi-Z
High-Order Address
High-Order Address
Data (Input)
Data
Hi-Z
Hi-Z