CY8CTMG200-32LQXI Datasheet, PDF (125/309 Pages) Cypress Semiconductor – Technical Reference Manual (TRM)

I2C Slave
15.3.8 I2C_BUF Register
Address
Name
0,CFh
I2C_BUF
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Data Buffer[7:0]
Bit 2
Bit 1
Bit 0
Access
RW : 00
The I²C Data Buffer Register (I2C_BUF) is the CPU read/
write interface to the data buffer. Whenever this register is
read, the data at the location pointed to by the CPU current
pointer (CPU_CP) is returned. Similarly, whenever this reg-
ister is written, the data is transferred to the buffer and writ-
ten at the location pointed to by the CPU current pointer
(CPU_CP). Whenever this register is read, without initializ-
ing the RAM contents either through the I²C or CPU inter-
face, no valid value is returned.
The M8C accesses the data buffer through this register
interface (I2C_BUF). Since the M8C issues an I/O read sig-
nal before an I/O write for some opcodes, the pointers
(CPU_CP) to the data buffer increment unnecessarily
because of an extra I/O read before an I/O write. Hence, all
the I/O reads that occur in FIRST phase are ignored. The I/
O reads that occur only in EXEC phase are taken as actual
I/O reads for this register.
So, only the following basic M8C register access instruc-
tions may be used for accessing this register:
MOV A, reg[expr]
MOV A, reg[X+expr]
MOV [expr], [expr]
MOV reg[expr], A
MOV reg[X+expr], A
MOV reg[expr], expr
MOV reg[X+expr], expr
Note When in compatibility mode, this register is not in use.
Bits 7 to 0: Data Buffer[7:0]. The I²C Data Buffer Regis-
ter (I2C_BUF) is the CPU read/write interface to the data
buffer. Whenever this register is read, the data at the loca-
tion pointed to by the CPU current pointer (CPU_CP) is
returned. Similarly, whenever this register is written, the
data is transferred to the buffer and written at the location
pointed to by the CPU current pointer (CPU_CP). Whenever
this register is read, without initializing the RAM contents
either through the I²C or CPU interface, no valid value is
returned.
For additional information, refer to the I2C_BUF register on
page 233.
PSoC CY8CTMG20x and CY8CTST200 TRM, Document No. 001-53603 Rev. *C
125
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