cp3ub26 National Semiconductor Corporation, cp3ub26 Datasheet - Page 29

• Manufacturer Part Number: cp3ub26
• Description: Reprogrammable Connectivity Processor With Usb And Can Interfaces
• Manufacturer: National Semiconductor Corporation

7.0
The system configuration registers control and provide sta-
tus for certain aspects of device setup and operation, such
as indicating the states sampled from the ENV[2:0] inputs.
The system configuration registers are listed in Table 9.
7.1
The MCFG register is a byte-wide, read/write register that
selects the clock output features of the device.
At reset, the register bits are cleared except for the
USB_ENABLE bit, which is set. Initialization software must
write a specific value to this register to enable the SCLK,
MCLK, output pin function.
The register must be written in active mode only, not in pow-
er save, HALT, or IDLE mode. However, the register con-
tents are preserved during all power modes.
The MCFG register format is shown below.
EXIOE
PLLCLKOE
MCLKOE
SCLKOE
Res.
7
MSTAT
MCFG
Name
MEM_IO
_SPEED
Table 9 System Configuration Registers
6
System Configuration Registers
MODULE CONFIGURATION REGISTER
(MCFG)
The EXIOE bit controls whether the external
bus is enabled in the IRE environment for im-
plementing the I/O Zone (FF FB00h
FBFFh).
0
1
The PLLCLKOE bit controls whether the PLL
clock is driven on the ENV0/PLLCLK pin.
0
1
The MCLKOE bit controls whether the Main
Clock is driven on the ENV1/CPUCLK pin.
0
1
The SCLKOE bit controls whether the Slow
Clock is driven on the ENV2/SLOWCLK pin.
0
1
MISC_IO
_SPEED
–
–
–
–
–
–
–
–
External bus disabled.
External bus enabled.
ENV0/PLLCLK pin is high impedance.
PLL clock driven on the ENV0/PLLCLK
pin.
ENV1/CPUCLK pin is high impedance.
Main Clock is driven on the ENV1/CPU-
CLK pin.
ENV2/SLOWCLK pin is high impedance.
Slow Clock is driven on the ENV2/SLOW-
CLK pin.
5
FF F910h
FF F914h
Address
_ENABLE
USB
4
SCLK
OE
3
Module Configuration
Module Status
MCLK
Description
OE
2
Register
Register
PLLCLK
OE
1
–
EXI
OE
0
FF
29
USB_ENABLE The USB_ENABLE bit can be used to force
MISC_IO_SPEED The MISC_IO_SPEED bit controls the slew
MEM_IO_SPEED The MEM_IO_SPEED bit controls the slew
an external USB transceiver into its low-power
mode. The power mode is dependent on the
USB controller status, the USB_ENABLE bit
in the Function Word (see Section 8.4.1), and
the USB_ENABLE bit in the MCFG register.
0
1
rate of the output drivers for the ENV[2:0],
RDY, and TDO pins. To minimize noise, the
slow slew rate is recommended.
0
1
rate of the output drivers for the A[22:0], RD,
SEL[2:0], SELIO, WR[1:0], PB[7:0], and
PC[7:0] pins. Memory speeds for the
CP3UB26 are characterized with fast slew
rate. Slow slew rate reduces the available
memory access time by 5 ns.
0
1
–
–
–
–
–
–
External USB transceiver forced into low-
power mode.
Transceiver power mode dependent on
USB controller status and programming
of the Function Word. (This is the state of
the USB_ENABLE bit after reset.)
Fast slew rate.
Slow slew rate.
Fast slew rate.
Slow slew rate.
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