RX64M_15 Datasheet, PDF (70/230 Pages) Renesas Technology Corp – Renesas MCUs

RX64M Group
4. I/O Registers
4. I/O Registers
This section gives information on the on-chip I/O register addresses. The information is given as shown below. Notes on
writing to registers are also given at the end.
(1) I/O register addresses (address order)
 Registers are listed from the lower allocation addresses.
 Registers are classified according to module symbols.
 The number of access cycles indicates the number of cycles based on the specified reference 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
R01DS0173EJ0100 Rev.1.00
Jul 31, 2014
Page 70 of 230