M30622MA-XXXFP RENESAS [Renesas Technology Corp], M30622MA-XXXFP Datasheet - Page 526

• Manufacturer Part Number: M30622MA-XXXFP
• Description: 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY
• Manufacturer: RENESAS [Renesas Technology Corp]

External Buses
Figure 5.2.3. Chip select control register
5.2.3 Bus Types
5.2.4 R/W Modes
The M16C/62 Group has two types of buses: a separate bus where separate pins are used for address
output and data input/output and a multiplexed bus where pins are time- multiplexed and switched be-
tween address output and data input/output to save the number of pins used.
A separate bus is used to access devices such as ROM and RAM which have separate buses. The areas
accessed via separate buses can be allocated for programs and data.
A multiplexed bus is used to access devices such as ASSPs which have multiplexed buses. The areas
accessed via a multiplexed bus can only be allocated for data. Programs cannot be located in these areas.
The area accessed via a multiplex bus can be selected from three types of area CS2 area, CS1 area, and
entire space by setting the multiplexed bus select bits (bits 4 and 5) of the processor mode register 0 (address
0004
Areas not accessed via multiplexed bus are accessed through separate buses.
When accessing an area set for access via a multiplexed bus the data bus is 8 bits wide, the data bus D
to D
If the data bus is 16 bits wide, the data bus D
case, the bus is switched between data and address separated only in time.
In the latter case, however, the addresses of connected devices are mapped into even addresses (every
other addresses) of the M16C/62. Therefore, be sure to access the M16C/62's even addresses in length
of bytes when accessing a connected device.
The read/write signal that is output when accessing an external area can be selected between the RD/
BHE/WR and the RD/WRH/WRL modes by setting the R/W mode select bit (bit 2) of the processor mode
register 0 (address 0004
________
WRL mode to access an 8-bit wide RAM.
When the M16C/62 is reset, the RD/BHE/WR mode is selected by default. To switch over the R/W mode,
change the RD/BHE/WR to the RD/WRH/WRL mode before accessing an external RAM.
Refer to the connection examples of RD/BHE/WR and RD/WRH/WRL shown in Section 5.4, "Connection
Examples."
_______ ______
7
16
Chip select control register
is multiplexed with address bus A
). However, the entire space cannot be selected when operating in the microprocessor mode.
b7
b6
_____ ________ ______
b5
b4
b3
_____ _________ ________
b2
b1
16
b0
). Use the RD/BHE/WR mode to access a 16-bit wide RAM and the RD/WRH/
Bit symbol
CS0
CS1
CS2
CS3
CS0W
CS1W
CS2W
CS3W
Symbol
CSR
_____ ________ ______
_____ _________ ________
_____ ________ ______
_____ ________ ______
CS0 output enable bit
CS1 output enable bit
CS2 output enable bit
CS3 output enable bit
CS0 wait bit
CS1 wait bit
CS2 wait bit
CS3 wait bit
0
to A
Bit name
7
0
.
to D
Address
0008
7
16
is multiplexed with address bus A
_____ _________ ________
When reset
0 : Chip select output disabled
1 : Chip select output enabled
0 : Wait state inserted
1 : No wait state
01
(Normal port pin)
16
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Function
_______
R
Mitsubishi microcomputers
M16C / 62 Group
W
1
to A
______
8
. In either
_____ _________
_____
511
0