UPD78F0890GK(A)-GAJ-AX NEC, UPD78F0890GK(A)-GAJ-AX Datasheet - Page 460

• Manufacturer Part Number: UPD78F0890GK(A)-GAJ-AX
• Description: 8BIT MCU, 128K FLASH, 7K RAM, LQFP
• Manufacturer: NEC

Specifications of UPD78F0890GK(A)-GAJ-AX

• Controller Family/series: UPD78F
• No. Of I/o's: 55
• Ram Memory Size: 7KB
• Cpu Speed: 20MHz
• No. Of Timers: 10
• No. Of Pwm: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 128KB
• Oscillator Type: External, Internal

16.9.3 Receive history list function
in which each data frame or remote frame was received and stored. The RHL consists of storage elements equivalent
to up to 23 messages, the last in-message pointer (LIPT) with the corresponding C0LIPT register and the receive
history list get pointer (RGPT) with the corresponding C0RGPT register.
operation modes.
reading the C0LIPT register, therefore, the number of the message buffer that received and stored a data frame or
remote frame first can be checked. The LIPT pointer is utilized as a write pointer that indicates to what part of the
RHL a message buffer number is recorded. Any time a data frame or remote frame is received and stored, the
corresponding message buffer number is recorded to the RHL element indicated by the LIPT pointer. Each time
recording to the RHL has been completed, the LIPT pointer is automatically incremented. In this way, the number of
the message buffer that has received and stored a frame will be recorded chronologically.
pointer indicates the first RHL element that the CPU has not read yet. By reading the C0RGPT register by software,
the number of a message buffer that has received and stored a data frame or remote frame can be read. Each time a
message buffer number is read from the C0RGPT register, the RGPT pointer is automatically incremented.
match) of the C0RGPT register is set to 1. This indicates that no message buffer number that has not been read
remains in the RHL. If a new message buffer number is recorded, the LIPT pointer is incremented and because its
value no longer matches the value of the RGPT pointer, the RHPM bit is cleared. In other words, the numbers of the
unread message buffers exist in the RHL.
history list overflow) of the C0RGPT register is set to 1. This indicates that the RHL is full of numbers of message
buffers that have not been read. When further message reception and storing occur, the last recorded message
buffer number is overwritten by the number of the message buffer that received and stored the new message. In this
case, after the ROVF bit has been set (1), the recorded message buffer numbers in the RHL do not completely reflect
the chronological order. However messages itself are not lost and can be located by CPU search in message buffer
memory with the help of the DN-bit.
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The receive history list (RHL) function records in the receive history list the number of the receive message buffer
The RHL is undefined immediately after the transition of the CAN module from the initialization mode to one of the
The C0LIPT register holds the contents of the RHL element indicated by the value of the LIPT pointer minus 1. By
The RGPT pointer is utilized as a read pointer that reads a recorded message buffer number from the RHL. This
If the value of the RGPT pointer matches the value of the LIPT pointer, the RHPM bit (receive history list pointer
If the LIPT pointer is incremented and matches the value of the RGPT pointer minus 1, the ROVF bit (receive
Caution
If the history list is in the overflow condition (ROVF is set), reading the history list contents is
still possible, until the history list is empty (indicated by RHPM flag set). Nevertheless, the
history list remains in the overflow condition, until ROVF is cleared by software. If ROVF is not
cleared, the RHPM flag will also not be updated (cleared) upon a message storage of newly
received frame. This may lead to the situation, that RHPM indicates an empty history list,
although a reception has taken place, while the history list is in the overflow state (ROVF and
RHPM are set).
CHAPTER 16 CAN CONTROLLER
User’s Manual U17554EJ4V0UD