Bidirectional Data Registers 0 To 15 (Twr0 To Twr15); Status Registers 1 To 4 (Str1 To Str4) - Renesas H8S/2100 Series Hardware Manual

Section 20 LPC Interface (LPC)

20.3.11 Bidirectional Data Registers 0 to 15 (TWR0 to TWR15)

TWR0 to TWR15 are sixteen 8-bit readable/writable registers to both the slave (this LSI) and host.
In TWR0, however, two registers (TWR0MW and TWR0SW) are allocated to the same address
for both the host and the slave addresses. TWR0MW is a write-only register for the host, and a
read-only register for the slave, while TWR0SW is a write-only register for the slave and a read-
only register for the host. When the host and slave begin a write, after the respective registers of
TWR0 have been written to, arbitration for simultaneous access is performed by checking the
status flags whether or not those writes were valid. For the registers selected from the host
according to the I/O address, see section 20.3.7, LPC Channel 3 Address Registers H and L
(LADR3H and LADR3L).
Data transferred in an LPC I/O write cycle is written to the selected register; in an LPC I/O read
cycle, the data in the selected register is transferred to the host. The initial values of TWR0 to
TWR15 are H'00.

20.3.12 Status Registers 1 to 4 (STR1 to STR4)

STR1 to STR4 are 8-bit registers that indicate status information during LPC interface processing.
The registers selected from the host according to the I/O address are shown in the following table.
In an LPC I/O read cycle, the data in the selected register is transferred to the host.
Bits 15 to 4 Bit 3
Bits 15 to 4 Bit 3
n = 1 to 4
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I/O Address
Bit 2 Bit 1
1 Bit1
Transfer
Bit 0 Cycle
Bit 0 I/O read
Host Register Selection
STRn read