4524 Datasheet, PDF (52/161 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4524 Group
SERIAL I/O
The 4524 Group has a built-in clock synchronous serial I/O which
can serially transmit or receive 8-bit data.
Serial I/O consists of;
• serial I/O register SI
• serial I/O control register J1
• serial I/O transmit/receive completion flag (SIOF)
• serial I/O counter
Registers A and B are used to perform data transfer with internal
CPU, and the serial I/O pins are used for external data transfer.
The pin functions of the serial I/O pins can be set with the register
J1.
Table 14 Serial I/O pins
Pin
D6/SCK
D5/SOUT
D4/SIN
Pin function when selecting serial I/O
Clock I/O (SCK)
Serial data output (SOUT)
Serial data input (SIN)
Note: Even when the SCK, SOUT, SIN pin functions are used, the input of
D6, D5, D4 are valid.
1/8
1/4
INSTCK
1/2
D6/SCK ^SCK
D5/SOUT ^SOUT
J13J12
00
01
10
11
Synchronous
circuit
Serial I/O counter (3)
QS
R
SIN
D4/SIN
J11 J10
MSB Serial I/O register (8) LSB
TABSI
TSIAB
TABSI
Register B (4) Register A (4)
SIOF
Serial I/O
interrupt
SST
instruction
Internal reset signal
Fig. 38 Serial I/O structure
Table 15 Serial I/O control register
Serial I/O control register J1
at reset : 00002
at power down : state retained
J13 J12
Synchronous clock
J13
0 0 Instruction clock (INSTCK) divided by 8
Serial I/O synchronous clock selection bits 0 1 Instruction clock (INSTCK) divided by 4
J12
1 0 Instruction clock (INSTCK) divided by 2
1 1 External clock (SCK input)
J11 J10
Port function
J11
0 0 D6, D5, D4 selected/SCK, SOUT, SIN not selected
Serial I/O port function selection bits
J10
0 1 SCK, SOUT, D4 selected/D6, D5, SIN not selected
1 0 SCK, D5, SIN selected/D6, SOUT, D4 not selected
1 1 SCK, SOUT, SIN selected/D6, D5, D4 not selected
Note: “R” represents read enabled, and “W” represents write enabled.
R/W
TAJ1/TJ1A
Rev.2.00 Jul 27, 2004 page 52 of 159
REJ03B0091-0200Z