MC68HC705JJ7 Datasheet, PDF (99/164 Pages) Freescale Semiconductor, Inc – Microcontrollers

SIOP Registers
Table 9-1. SIOP Clock Rate Selection
SPR1
0
0
1
1
SPR0
0
1
0
1
SIOP Clock Rate
Oscillator Frequency
Divided by:
64
32
16
8
9.3.2 SIOP Status Register
The SIOP status register (SSR) is located at address $000B and contains two read-only bits. Figure 9-5
shows the position of each bit in the register and indicates the value of each bit after reset.
Address: $000B
Bit 7
6
5
4
3
2
1
Bit 0
Read: SPIF
DCOL
0
0
0
0
0
0
Write:
Reset:
0
0
0
0
0
0
0
0
= Unimplemented
Figure 9-5. SIOP Status Register (SSR)
SPIF — Serial Port Interrupt Flag
The SPIF is a read-only status bit that is set on the last rising edge of SCK and indicates that a data
transfer has been completed. It has no effect on any future data transfers and can be ignored. The
SPIF bit can be cleared by reading the SSR followed by a read or write of the SDR or by writing a logic
1 to the SPIR bit in the SCR. If the SPIF is cleared before the last rising edge of SCK it will be set again
on the last rising edge of SCK. Reset clears the SPIF bit.
1 = Serial transfer complete, serial interrupt if the SPIE bit in SCR is set
0 = Serial transfer in progress or serial interface idle
DCOL — Data Collision Bit
The DCOL is a read-only status bit which indicates that an illegal access of the SDR has occurred. The
DCOL bit will be set when reading or writing the SDR after the first falling edge of SCK and before SPIF
is set. Reading or writing the SDR during this time will result in invalid data being transmitted or
received. The DCOL bit is cleared by reading the SSR (when the SPIF bit is set) followed by a read or
write of the SDR. If the last part of the clearing sequence is
done after another transfer has started, the DCOL bit will be set again. Reset clears the DCOL bit.
1 = Illegal access of the SDR occurred
0 = No illegal access of the SDR detected
MC68HC705JJ7 • MC68HC705JP7 Advance Information Data Sheet, Rev. 4.1
Freescale Semiconductor
99