DF2505FC26V Renesas Electronics America, DF2505FC26V Datasheet - Page 111

• Manufacturer Part Number: DF2505FC26V
• Description: IC H8S/2505 MCU FLASH 144QFP
• Manufacturer: Renesas Electronics America
• Series: H8® H8S/2500r

Specifications of DF2505FC26V

• Core Processor: H8S/2000
• Core Size: 16-Bit
• Speed: 26MHz
• Connectivity: I²C, SCI
• Peripherals: POR, PWM, WDT
• Number Of I /o: 104
• Program Memory Size: 384KB (384K x 8)
• Program Memory Type: FLASH
• Ram Size: 32K x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 5.5 V
• Data Converters: A/D 16x10b; D/A 2x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 144-QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -

2.9.4
A read value from a write-only bit using a data-transfer or a bit-manipulation instruction is
undefined. To avoid using the read value for subsequent operations, follow the procedure shown
below to access registers that include write-only bits.
When writing to registers that include write-only bits, set up a work area in memory such as on-
chip RAM, write the data to the work area, read the data back from the memory, and then write
the data to the registers that include write-only bits.
I/O
P1DDR
After bit-
manipulation
I/O
P1DDR
Write value
The target bit of the data read out is then manipulated. In this example, clearing bit 4 of H'F8
leaves us with H'E8.
After the bit-manipulation, The data is then written back to P1DDR, and execution of the
BCLR instruction is complete.
This instruction was meant to change the value of P1DDR to H'E0, but H'E8 was written back
instead. P13, which should be an input pin, has been turned into an output pin. Note that while
the error in this case occurred because bit 3 in P1DDR was read as 1, the values read from bits
7 to 0 in P1DDR are undefined. Bit-manipulation instructions that write back values might
change any bit from 0 to 1 or 1 to 0. Section 2.9.4, Access Method for Registers with Write-
Only Bits, describes a way to avoid this possibility when changing the values of registers that
include write-only bits.
The BCLR instruction can be used to clear flags in the internal I/O registers to 0. In this case,
if it is obvious that a given flag has been set to 1 because an interrupt handler has been entered,
there is no need to read the flag .
Access Method for Registers with Write-Only Bits
Output
Output
P17
P17
1
1
1
1
Output
Output
P16
P16
1
1
1
1
Output
Output
P15
P15
1
1
1
1
Output
Input
P14
P14
1
0
0
0
Output
Input
P13
P13
0
1
1
1
Rev. 6.00 Sep. 24, 2009 Page 63 of 928
Input
Input
P12
P12
0
0
0
0
Input
Input
P11
P11
REJ09B0099-0600
0
0
0
0
Section 2 CPU
Input
Input
P10
P10
0
0
0
0