Renesas ZTAT H8S/2357F, Hardware Manual

Page: 210 / 1047

Rev.6.00 Oct.28.2004 page 182 of 1016
REJ09B0138-0600H
(1) Normal Mode
ETCRA
Transfer Counter
Bit : 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ETCR :
Initial value : * * * * * * * * * * * * * * * *
R/W : R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W
* : Undefined
In normal mode, ETCRA functions as a 16-bit transfer counter. ETCRA is decremented by 1 each time a transfer is
performed, and transfer ends when the count reaches H'0000. ETCRB is not used at this time.
ETCRB
ETCRB is not used in normal mode.
(2) Block Transfer Mode
ETCRA
Holds block size
Bit : 15 14 13 12 11 10 9 8
ETCRAH :
Initial value :
* * * * * * * *
R/W : R/W R/W R/W R/W R/W R/W R/W R/W
Block size counter
Bit : 7 6 5 4 3 2 1 0
ETCRAL :
Initial value :
* * * * * * * *
R/W : R/W R/W R/W R/W R/W R/W R/W R/W
*
: Undefined
ETCRB
Block Transfer Counter
Bit : 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ETCRB :
Initial value :
* * * * * * * * * * * * * * * *
R/W : R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W
In block transfer mode, ETCRAL functions as an 8-bit block size counter and ETCRAH holds the block size. ETCRAL is
decremented each time a 1-byte or 1-word transfer is performed, and when the count reaches H'00, ETCRAL is loaded
with the value in ETCRAH. So by setting the block size in ETCRAH and ETCRAL, it is possible to repeatedly transfer
blocks consisting of any desired number of bytes or words.
ETCRB functions in block transfer mode, as a 16-bit block transfer counter. ETCRB is decremented by 1 each time a
block is transferred, and transfer ends when the count reaches H'0000.