4502 Datasheet, PDF (47/116 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4502 Group
(5) External clock
When the external signal clock is used as the source oscillation
(f(XIN)), connect the XIN pin to the clock source and leave XOUT pin
open. Then, execute the CMCK instruction (Figure 47).
Be careful that the maximum value of the oscillation frequency
when using the external clock differs from the value when using the
ceramic resonator (refer to the recommended operating condition).
Also, note that the RAM back-up mode (POF and POF2 instruc-
tions) cannot be used when using the external clock.
(6) Clock control register MR
Register MR controls system clock. Set the contents of this register
through register A with the TMRA instruction. In addition, the TAMR
instruction can be used to transfer the contents of register MR to
register A.
Table 19 Clock control register MR
4502
* Execute the CMCK
instruction in program.
XIN
XOUT ^VDD
VSS
External oscillation circuit
Fig. 47 External clock input circuit
Clock control register MR
at reset : 11002
at RAM back-up : 11002
MR3
MR2
System clock selection bits
MR1 Not used
MR0 Not used
MR3 MR2
System clock
0 0 f(XIN) (high-speed mode)
0 1 f(XIN)/2 (middle-speed mode)
1 0 f(XIN)/4 (low-speed mode)
1 1 f(XIN)/8 (default mode)
0
1
This bit has no function, but read/write is enabled.
0
1
This bit has no function, but read/write is enabled.
Note : “R” represents read enabled, and “W” represents write enabled.
R/W
ROM ORDERING METHOD
Please submit the information described below when ordering
Mask ROM.
(1) Mask ROM Order Confirmation Form ..................................... 1
(2) Data to be written into mask ROM ............................... EPROM
(three sets containing the identical data)
(3) Mark Specification Form .......................................................... 1
✽For the mask ROM confirmation and the mark specifications,
refer to the “Renesas Technology Corp.” Homepage
(http://www.renesas.com/en/rom).
Rev.3.01 2005.02.02 page 47 of 112
REJ03B0105-0301