
II CORE BLOCK: BCU (Bus Control Unit)
S1C33T01 FUNCTION PART
EPSON
B-II-4-47
PLL_CLK:
PLL output clock. This clock is stable and kept as output except in the following cases:
1. When the PLL is off by setting the PLLS[1:0] pins.
2. When the OSC3 (high-speed) oscillation is stopped by executing the SLP instruction.
3. When the OSC3 (high-speed) oscillation is stopped using the CLG register.
Note that the PLL_CLK clock is out of phase with the CPU operating clock.
OSC3_CLK: OSC3 (high-speed) oscillation circuit output clock. This clock is stable and kept as output except in the
following cases:
1. When the OSC3 (high-speed) oscillation is stopped by executing the SLP instruction.
2. When the OSC3 (high-speed) oscillation is stopped using the CLG register.
Note that the OSC3_CLK clock is out of phase with the CPU operating clock.
BCU_CLK: Bus clock in the bus controller. This clock varies according to the bus cycle speed. Furthermore, the
clock frequency changes dynamically in x2 speed mode as follows:
1. When the internal RAM/ROM is accessed, x2 clock (e.g., 50 MHz same as the CPU operating
clock) is output.
2. When an external device is accessed via the external bus, x1 clock (e.g., 25 MHz) is output.
This dynamic change (e.g., between 50 MHz and 25 MHz) does not affect the external memory access
timing, such as position relationship between the rising or falling edge of the 25 MHz clock and the
falling edge of the #WR signal. (It is the same as that in the x1 speed mode with 25 MHz clock.)
CPU_CLK: The CPU operating clock. The clock frequency is as follows:
1. Equals to the PLL output clock frequency when the PLL is on.
2. Equals to the OSC3 (high-speed) oscillation circuit output clock frequency when the PLL is off.
3. However, it equals to the divided frequency when the CLG is set to generate the CPU operating
clock by dividing the source clock.
4. When the CPU stops by the HALT or SLP instruction, this clock is also stopped.
This clock is almost in phase with the bus clock.
At initial reset, BCLKSEL is set to "0" (CPU_CLK).
A1X1MD: Area 1 access speed (D3) / BCLK select register (0x4813A)
Select a number of access cycles for area 1 in x2 speed mode.
Write "1": 2 cycles
Write "0": 4 cycles
Read: Valid
When x2 speed mode is set (#X2SPD pin = L) and A1X1MD = "1", area 1 is read/written in 2 cycles of the CPU
system clock.
When A1X1MD = "0", area 1 is read/written in 4 cycles.
When x1 speed mode is set (#X2SPD pin = H), area 1 is always accessed in 2 cycles regardless of the A1X1MD
value.
At cold start, A1X1MD is set to "0" (4 cycles). At hot start, A1X1MD retains its status before being initialized.
A18RH: Areas 17 and 18 read hold cycle insertion (D7) / Read cycle hold time control register (0x4813C)
A16RH: Areas 15 and 16 read hold cycle insertion (D6) / Read cycle hold time control register (0x4813C)
A14RH: Areas 13 and 14 read hold cycle insertion (D5) / Read cycle hold time control register (0x4813C)
A12RH: Areas 11 and 12 read hold cycle insertion (D4) / Read cycle hold time control register (0x4813C)
A8RH:
Areas 7 and 8 read hold cycle insertion (D2) / Read cycle hold time control register (0x4813C)
A6RH:
Area 6 read hold cycle insertion (D1) / Read cycle hold time control register (0x4813C)
A5RH:
Area 5 read hold cycle insertion (D0) / Read cycle hold time control register (0x4813C)
Selects whether or not a read hold cycle is inserted in each area when accessed.
Write "1": Read hold cycle inserted
Write "0": No read hold cycle inserted
Read: Valid