71M6542F MAXIM [Maxim Integrated Products], 71M6542F Datasheet - Page 73

• Manufacturer Part Number: 71M6542F
• Description: 0.1% Accuracy Over 2000:1 Current Range Energy Meter ICs
• Manufacturer: MAXIM [Maxim Integrated Products]

2.5.10 SPI Slave Port
The slave SPI port communicates directly with the MPU data bus and is able to read and write Data RAM
and I/O RAM locations. It is also able to send commands to the MPU. The interface to the slave port
consists of the SPI_CSZ, SPI_CKI, SPI_DI and SPI_DO pins. These pins are multiplexed with the
combined DIO/LCD segment driver pins SEGDIO36 to SEGDIO39.
Additionally, the SPI interface allows flash memory to be read and to be programmed. To facilitate flash
programming, cycling power or asserting RESET causes the SPI port pins to default to SPI mode. The
SPI port is disabled by clearing the SPI_E bit (I/O RAM 0x270C[4]).
Possible applications for the SPI interface are:
1) An external host reads data from CE locations to obtain metering information. This can be used in
2) A communication link can be established via the SPI interface: By writing into MPU memory locations,
3) An external DSP can access front-end data generated by the ADC. This mode of operation uses the
4) Flash programming by the external host (SPI Flash Mode).
SPI Transactions
A typical SPI transaction is as follows. While SPI_CSZ is high, the port is held in an initialized/reset state.
During this state, SPI_DO is held in Hi-Z state and all transitions on SPI_CLK and SPI_DI are ignored.
When SPI_CSZ falls, the port begins the transaction on the first rising edge of SPI_CLK. As shown in
Table
followed by one or more bytes of data. The transaction ends when SPI_CSZ is raised. Some transactions
may consist of a command only.
SDATA output Z
SDATA (output)
EECTRL Byte Written
SCLK (output)
Write -- With HiZ and WFR
applications where the 71M654x function as a smart front-end with preprocessing capability. Since
the addresses are in 16-bit format, any type of XRAM data can be accessed: CE, MPU, I/O RAM, but
not SFRs or the 80515-internal register bank.
the external host can initiate and control processes in the 71M654x MPU. Writing to a CE or MPU
location normally generates an interrupt, a function that can be used to signal to the MPU that the
byte that had just been written by the external host must be read and processed. Data can also be
inserted by the external host without generating an interrupt.
71M654x as an analog front-end (AFE).
Write -- No HiZ
62, a transaction consists of an optional 16 bit address, an 8 bit command, an 8 bit status byte,
BUSY (bit)
SDATA output Z
SDATA (out/in)
EECTRL Byte Written
SCLK (output)
BUSY (bit)
Figure 26: 3-wire Interface. Write Command when HiZ=1 and WFR=1.
Figure 25: 3-Wire Interface. Write Command when CNT=0
D7
INT5 not issued
(LoZ)
D7
CNT Cycles (0 shown)
D6
(From 654x)
CNT Cycles (6 shown)
(LoZ)
D5
SDATA output Z
SDATA (output)
EECTRL Byte Written
SCLK (output)
D4
BUSY (bit)
Write -- HiZ
71M6541D/F/G and 71M6542F/G Data Sheet
D3
D2
INT5 not issued
(From EEPROM)
(HiZ)
(HiZ)
BUSY
CNT Cycles (0 shown)
READY
INT5