RX220_15 Datasheet, PDF (25/107 Pages) Renesas Technology Corp – Renesas MCUs

RX220 Group
4. I/O Registers
4. I/O Registers
This section provides information on the on-chip I/O register addresses and bit configuration. The information is given as
shown below. Notes on writing to registers are also given below.
(1) I/O register addresses (address order)
 Registers are listed from the lower allocation addresses.
 Registers are classified according to module symbols.
 Numbers of cycles for access indicate numbers of cycles of the given base clock.
 Among the internal I/O register area, addresses not listed in the list of registers are reserved. Reserved addresses
must not be accessed. Do not access these addresses; otherwise, the operation when accessing these bits and
subsequent operations cannot be guaranteed.
(2) Notes on writing to I/O registers
When writing to an I/O register, the CPU starts executing the subsequent instruction before completing I/O register write.
This may cause the subsequent instruction to be executed before the post-update I/O register value is reflected on the
operation.
As described in the following examples, special care is required for the cases in which the subsequent instruction must be
executed after the post-update I/O register value is actually reflected.
[Examples of cases requiring special care]
 The subsequent instruction must be executed while an interrupt request is disabled with the IENj bit in IERn of the
ICU (interrupt request enable bit) cleared to 0.
 A WAIT instruction is executed immediately after the preprocessing for causing a transition to the low power
consumption state.
In the above cases, after writing to an I/O register, wait until the write operation is completed using the following
procedure and then execute the subsequent instruction.
(a) Write to an I/O register.
(b) Read the value from the I/O register to a general register.
(c) Execute the operation using the value read.
(d) Execute the subsequent instruction.
[Instruction examples]
 Byte-size I/O registers
MOV.L #SFR_ADDR, R1
MOV.B #SFR_DATA, [R1]
CMP [R1].UB, R1
;; Next process
 Word-size I/O registers
MOV.L #SFR_ADDR, R1
MOV.W #SFR_DATA, [R1]
CMP [R1].W, R1
;; Next process
R01DS0130EJ0110 Rev.1.10
Dec 20, 2013
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