7477 datasheet(120/354 Pages) RENESAS

120 / 354 page

HARDWARE

1-103

7470/7471/7477/7478 GROUP USER’S MANUAL

1.13 Serial I/O

Fig. 1.13A.8 Structure of Serial I/O counter and Byte counter

(2) Serial I/O counter, Byte counter (Address 00DE16)

The Serial I/O counter and the Byte counter are located at the same address.

q Serial I/O counter (bit 4 – bit 6)

The Serial I/O counter is set to “7” by writing transmit data into the Serial I/O register and counts

the synchronous clock of the Serial I/O eight times. The Serial I/O counter is a read-only type and

not affected by any write operation to the Byte counter.

q Byte counter (bit 0 – bit 3)

In the Serial I/O byte specification mode, the value written in the Byte counter is counted down at

8 cycles of the synchronous clock. When the value becomes “0,” a Serial I/O transmit/receive is

performed by the synchronous clock of the next 8 cycles. Because a reload function is not available,

re-set a value to transfer data continuously in the byte specification mode.

Figure 1.13A.8 shows a structure of the Serial I/O counter and the Byte counter.

b7 b6 b5 b4 b3 b2 b1 b0

Serial I/O counter and Byte counter [Address

Function

At reset

Serial I/O counter and Byte counter (7470/7471 group)

Byte counter

?? !

When using the byte specification mode, set

a value of “0016” to “0F16.” Supposing that the

value to be written into the byte counter is “n,”

a Serial transmit/receive is performed with the

clock of the “n + 1”-th byte.

Serial I/O counter

When the internal clock is selected as a

synchronous clock, this counter generates 8

shift clocks.

When transmit data is written into the Serial

I/O register, “07 16” is set in the Serial I/O

counter.

Nothing is allocated for this bit. This is write

disabled bit and is undefined at reading.

00DE16]

7477 Datasheet(PDF) 120 Page - Renesas Technology Corp