Read And Write Signals; Ale Signal - Renesas M16C/6NK Hardware Manual

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M16C/6N Group (M16C/6NK, M16C/6NM)

7.2.4 Read and Write Signals

When the data bus is 16-bit width, the read and write signals can be chosen to be a combination of RD,
______ ________
WR and BHE or a combination of RD, WRL and WRH by using the PM02 bit in the PM0 register. When
the data bus is 8-bit width, use a combination of RD, WR and BHE.
Table 7.3 shows the operation of RD, WRL, and WRH signals. Table 7.4 shows the operation of RD, WR,
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and BHE signals.
Table 7.3 Operation of RD, WRL and WRH Signals
Data Bus Width
16 Bits
(BYTE pin
input = L)
Table 7.4 Operation of RD, WR and BHE Signals
_____
Data Bus Width RD
16 Bits
(BYTE pin
input = L)
8 Bits
(BYTE pin input = H)

7.2.5 ALE Signal

The ALE signal latches the address when accessing the multiplexed bus space. Latch the address when
the ALE signal falls. Figure 7.3 shows the ALE signal, address bus and data bus.
When BYTE pin input = H
ALE
A0/D0 to A7/D7
A8 to A19
NOTE:
1. If the entire CS space is assigned a multiplexed bus, these pins function as I/O ports.
Figure 7.3 ALE Signal, Address Bus, Data Bus
Rev.2.00 Nov 28, 2005
REJ09B0124-0200
_____ ________
_____ ________
_____ ________ _________
_____ ________
RD WRL
L H
H L
H H
H L
_____ ______ ________
______ ________
WR BHE
H L L
L H L
H L H
L H H
H L L
L H L
H L Not used
L H Not used
Address Data
(1)
Address
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________
_____ ______ ________
_________
_________
WRH Status of External Data Bus
H Read data
H Write 1 byte of data to an even address
L Write 1 byte of data to an odd address
Write data to both even and odd addresses
L
Status of External Data Bus
A0
H Write 1 byte of data to an odd address
H Read 1 byte of data from an odd address
L Write 1 byte of data to an even address
L Read 1 byte of data from an even address
L Write data to both even and odd addresses
L Read data from both even and odd addresses
Write 1 byte of data
H to L
H to L Read 1 byte of data
When BYTE pin input = L
ALE
A0
Address
A1/D0 to A8/D7
A9 to A19
7. Bus
_____
_____ ______
Address
Data
Address