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CHAPTER 18 IEBus CONTROLLER (V850/SC2)
User’s Manual U15109EJ3V0UD
543
(12) IEBus communication count register (CCR)
The IEBus communication count register (CCR) indicates the number of remaining bytes in the communication
byte number specified in the communication mode.
Bits 7 to 0 of the IEBus communication count register (CCR) indicate the number of transfer bytes.
This register reads the count value of the counter that is preset to the maximum number of transmitted bytes
(32 bytes) per frame specified in mode 1 and is decremented during the ACK period of the data field
regardless of ACK/NACK. While SCR (IEBus success count register) is decremented upon normal
communication (ACK), CCR is decremented upon each 1-byte communication regardless of ACK/NACK.
When the count value has reached “00H”, the frame end flag (ENDFRAM) of the IEBus interrupt status register
(ISR) is set.
The maximum number of transfer bytes of the preset value of mode 1 per frame is 20H (32 bytes).
After reset: 20H
R
Address: FFFFF3F6H
7
6
5
4
3
2
1
0
CCR
(13) IEBus clock select register (IECLK)
This register selects the clock of the IEBus. The main clock frequencies that can be used are shown below.
Main clock frequencies other than the following cannot be used.
•
6.0 MHz/6.291 MHz
•
12.0 MHz/12.582 MHz
•
18.0 MHz/18.874 MHz
After reset: 00H
R/W
Address: FFFFF3F8H
7
6
5
4
3
2
1
0
IECLK
0
0
0
0
0
0
IECS1
IECS0
IECS1
IECS0
IEBus clock selection
0
0
@ f
XX
= 6.0 MHz or f
XX
= 6.291 MHz
0
1
@ f
XX
= 12.0 MHz or f
XX
= 12.582 MHz
1
×
@ f
XX
= 18.0 MHz or f
XX
= 18.874 MHz
Remark
×
: don’t care