Renesas Single-Chip Microcomputer M37531T-ADS Informacje Techniczne Pobierz pdf (Strona 44)

MESC TECHNICAL NEWS

No.M16C-55-0006

( 1 / 5)

GRADE

1. Affected devices

• M16C Family

2.Cautions

The registers shown in the table on the following page contain bits that will result in unknown data

when read.

If performing a read-modify-write sequence of instructions to a register with write only bits, please

reset the write only bits to their previous values before writing back to the register.

If your software accesses these registers frequently, please use a temporary RAM area to change

the value, and then transfer it to the register.

Figure 1 shows an example of a register structure. If you execute a ‘Read Modify Write’ instruction

like BSET, BCLR, AND or OR, the values of bits 5-7 may change. (Please see Figure 2)

‘Table 10’ show instruction table for Read Modify Write.

M16C Family

Cautions Using Data Registers that Include Write Only Bits

Timer A4 up/down flag

Timer A3 up/down flag

Timer A2 up/down flag

Timer A1 up/down flag

Timer A0 up/down flag

Timer A2 two-phase pulse

signal processing select bit

Timer A3 two-phase pulse

signal processing select bit

Timer A4 two-phase pulse

signal processing select bit

Symbol Address When reset

UDF 0384

TA4P

TA3P

TA2P

Up/down flag

Bit name FunctionBit symbol

b7 b6 b5 b4 b3 b2 b1 b0

TA4UD

TA3UD

TA2UD

TA1UD

TA0UD

0 : Down count

1 : Up count

This specification becomes valid

when the up/down flag content is

selected for up/down switching

cause

0 : two-phase pulse signal

processing disabled

1 : two-phase pulse signal

processing enabled

When not using the two-phase

pulse signal processing function,

set the select bit to “0”

Initial

data

0 0 0 0 0 0 0 0

b7 b0

In the case of initial data is “0”, set bit 0 to “1” with the use of

‘BSET’ instruction.

X X X 0 0 0 0 0

b7 b0

Read

Modify

Unknown

Data

X X X 0 0 0 0 1

b7 b0

X X X 0 0 0 0 1

b7 b0

Write

Different from initial data

The condition

after

executed

BSET

instruction

Figure 1. Example of a register structure

Figure 2. Example of a register change

Can not read these bits

Related to M16C/80, M16C/60, M16C/20 series devices.

1 2 ... 39 40 41 42 43 44 45 46 47 48 49 ... 56 57

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