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Control Registers and RAM
Multi-Buffer Serial Peripheral Interface (MibSPI) (SPNU217B)
95
7.30
Multi-buffer RAM
The multi-buffer RAM comprises all buffers, which can be configured
identically. The buffers can be partitioned into multiple transfer groups, each
containing a variable number of buffers. Each of the buffers can be sub-
divided into a 16-bit transmit field, a 16-bit receive field, a 16-bit control field
and a 16-bit status field, as displayed in Figure 19.
Figure 19.
Multi-buffer RAM Configuration
The MibSPI RAM location is set by one of the memory chip select within the
decoder. The corresponding SMCR register should be programmed to match
the number of wait-state required (see section 7.2). The different fields can
be read and written 8-bit, 16-bit or 32-bit wide.
The transmit fields can be written and read in the address range 000h to
1FDh. The control field array can be written and read in the address range
002h to 1FFh, i.e. the transmit fields are interleaved with the control fields.
When performing a 32-bit access the transmit field and the control field can
be accessed in parallel. The low half-word (xxxx xx00b) is allocated by the
transmit field and the high half-word (xxxx xx10b) is allocated by the
corresponding control field.
The receive fields are read-only and can be accessed through the address
range 202h to 3FFh. The corresponding status fields are mapped into the
same address range (200h to 3FDh), i.e. the receive fields are interleaved
with the status fields. When performing a 32-bit read from a receive buffer, the
high half-word contains the corresponding status information and the low
half-word comprises the receive data.
The chip select number bit field CSNR[5:0] of the control field is mirrored into
the status field after transmission.
The actual size of the multi-buffer RAM is implementation dependent. E.g. an
implementation of 16 buffers would consume 4*16*2 bytes = 128 bytes.
000h
Control 0
004h
Control 1
008h
Control 2
00Ch
Control 3
....
1F8h Control 126
1FCh Control 127
002h
Transmit 0
006h
Transmit 1
00Ah
Transmit 2
00Eh
Transmit 3
....
1FAhTransmit 126
1FEhTransmit 127
200h
Status 0
204h
Status 1
208h
Status 2
20Ch
Status 3
....
3F8h Status 126
3FCh Status 127
202h
Receive 0
206h
Receive 1
20Ah
Receive 2
20Eh
Receive 3
....
3FAh Receive 126
3FEh Receive 127
Buffer 0
1
2
3
...
126
127
addr. bit15 bit0
addr. bit31
bit16
Transmit field
Control field
32-bit write access from host
addr. bit15
bit0
addr. bit31
bit16
Status field
Receive field
32-bit read access from host
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