R8A77800ANBGAV Renesas Electronics America, R8A77800ANBGAV Datasheet - Page 445

• Manufacturer Part Number: R8A77800ANBGAV
• Description: IC SUPERH MPU ROMLESS 449-BGA
• Manufacturer: Renesas Electronics America
• Series: SuperH® SH7780r

Specifications of R8A77800ANBGAV

• Core Processor: SH-4A
• Core Size: 32-Bit
• Speed: 400MHz
• Connectivity: Audio Codec, MMC, Serial Sound, SCI, SIO, SPI, SSI
• Peripherals: DMA, POR, WDT
• Number Of I /o: 75
• Program Memory Type: ROMless
• Ram Size: 16K x 8
• Voltage - Supply (vcc/vdd): 1.15 V ~ 1.35 V
• Oscillator Type: External
• Operating Temperature: -20°C ~ 75°C
• Package / Case: 449-BGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Program Memory Size: -
• Data Converters: -

Section 11 Local Bus State Controller (LBSC)
11.5.8
Wait Cycles between Accesses
A problem associated with higher operating frequencies for external memory buses is that the data
buffer turn-off after completion of a read from a low-speed device may be too slow, causing a
collision with the data in the next access, and resulting in lower reliability or malfunctions. To
prevent this problem, this module provides a data collision prevention function. It stores the
preceding access area and the type of read/write and inserts a wait cycle before the access cycle if
there is a possibility of a bus collision when the next access is started. The process for wait cycle
insertion consists of inserting idle cycles between the access cycles as shown in section 11.4.3,
CSn Bus Control Register (CSnBCR). If bits IWW, IWRWD, IWRWS, IWRRD and IWRRS in
CSnBCR (n = 0 to 2 and 4 to 6) are used to set the number of idle cycles between accesses, the
number of inserted idle cycles is only the specified number of idle cycles minus the number of idle
cycles specified by the bits.
When bus arbitration is performed, the bus is released after wait cycles are inserted between the
cycles.
When a DMA transfer is performed, wait cycles are inserted as set in CSnBCR idle cycle bits.
When access the MPX interface area continuously after read access, 1 wait cycle is inserted even
if set the wait cycle to 0.
When the access size is 8-byte or 16-byte, wait cycles are inserted every 4-byte access.
Rev.1.00 Dec. 13, 2005 Page 393 of 1286
REJ09B0158-0100